ID |
Date |
Author |
Type |
Category |
Subject |
15082
|
Fri Dec 6 17:49:46 2019 |
rana | Summary | PEM | Jump test of seismometers: EX needs recentering |
Yehonathan, please center the EX seismometer.
The attached PDF shows the seismometer signals (I'm assuming that they're already calibrated into microns/s) during the lab tour for the art students on 11/1. The big spike which I've zoomed in on shows the time when we were in the control room and we all jumped up at the same time. There were approximately 15 students each with a mass of ~50-70 kg. I estimate that out landing times were all sync'd to within ~0.1 s. |
Attachment 1: Seismometers.pdf
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Attachment 2: src.tgz
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15083
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Sun Dec 8 20:15:41 2019 |
rana | Summary | PEM | Jump test of seismometers: EX needs recentering |
I have re-centered the EX (and EY) seismometers. They are Guralp CMG40-T, and have no special centering procedure except cycling the power a few times. I turned off the power on their interface box, then waited 10s before turning it back on.
The fist atm shows the comparison using data from 8-9 PM Saturday night:
- there seems to be a factor of 2 calibration diff between the T240 near the BS, and the Guralp seismometers at the end. Which one is right?
When was the last time they were cross calibrated?
- The low coherence between BS_X and EX_X shows the problem. They should be very coherent (> 0.9) for 0.1-1 Hz.

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Attachment 1: seis_all_191208.pdf
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15086
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Mon Dec 9 13:08:24 2019 |
Yehonathan | Summary | PEM | Jump test of seismometers: EX needs recentering |
I check the seismometers in the last 14 hours (Attached). Seems like the coherenece is restored in the x direction.
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Attachment 1: seis_191208.pdf
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15162
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Tue Jan 28 08:26:53 2020 |
rana | Frogs | PEM | shaking |
https://breakthrough.caltech.edu/magazine/2019-aug/#article-Listening-with-Light

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15313
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Fri Apr 24 00:26:59 2020 |
rana | Summary | PEM | L.A. EQ from Tuesday night |
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Attachment 1: April22-EQ.pdf
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15445
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Wed Jul 1 12:50:40 2020 |
gautam | Update | PEM | MC1 accelerometers plugged in |
I re-connected the 3 accelerometers located near the MC1/MC3 chamber. It was a bit tedious to get the cabling sorted - I estimate the cable is ~80m long, and the excess length had to be wound around a spool (see Attachment #1), which wasn't really a 1 person job. It's neat-ish for now, but I'm not entirely satisfied. I think we should get shorter cables (~20m), and also mount the pre-amp/power units in a rack instead of leaving it on the floor. The pre-amp settings are x100 for all three channels. The MC2 channels are powered, but are unconnected to the seismometers - it was too tedious to unroll the other spool yesterday. Apart from this, the cable for the "Z" channel had to be re-seated in the strain relief clamp.
I did not enable any of the CDS filters that convert the raw signal into physical units, so for now, these channels are just recording raw counts.
Update 7pm: the spectra in the current config are here - not sure what to make of the MC2_Z channel appearing to show lower noise?
Update July 13 2020 430pm: This afternoon, I hooked up the MC2 accelerometer channels too... |
Attachment 1: IMG_8617.JPG
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Attachment 2: IMG_8616.JPG
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15634
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Mon Oct 19 15:40:02 2020 |
Koji | Update | PEM | Alaska EQ M7.5 |
Alaska M7.5 20:54UTC https://earthquake.usgs.gov/earthquakes/eventpage/us6000c9hg/executive
I looked at the suspensions. The watchdogs have not been tripped.
IMC was locked but continually shaken. (and occasional unlock) |
15642
|
Fri Oct 23 19:01:57 2020 |
Koji | Summary | PEM | PSL Particle Counter kit removed from the table |
The particle counter on the 40m PSL was removed. The package was made together with the OMC lab particle counter (see the packing list below).
The kit was picked up by Radhika for a python code to read out the numbers.
=== Packing List ===
- MET ONE 227A particle counter
- used at the 40m. It has the particle reading and the temperature reading.
- Power supply adapter (AC/DC) for 227A
- Caution: It is not compatible with GT-321.
- MET ONE GT-321
- I found another type of particle counter in West Bridge.
- Power supply adapter (AC/DC) for GT-321. (Labeled "for GT-321")
- Caution: It is not compatible with 227A.
- DB9 cable for GT-321
- Air Filter G3111
- When you run a particle counter attach this filter instead of the dust collecting cup to keep the air in take of the particle counter clean. This should keep the particle level down to zero.
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Attachment 1: P_20201022_173529.jpg
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Attachment 2: P_20201022_173419.jpg
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15863
|
Thu Mar 4 15:48:26 2021 |
Koji | Summary | PEM | Watchdog tripped, Optics damped back |
EQs seen on Summary pages
https://nodus.ligo.caltech.edu:30889/detcharsummary/day/20210304/pem/seismic_blrms/ |
16214
|
Fri Jun 18 14:53:37 2021 |
Anchal | Summary | PEM | Temperature sensor network proposal |
I propose we set up a temperature sensor network as described in attachment 1.
Here there are two types of units:
- BASE-GATEWAY
- Holds the processor to talk to the network through Modbus TCP/IP protocol.
- This unit itself has a temperature sensor in it. It is powered by a power adaptor or PoE from the switch.
- Each base unit can have at max 2 extended temperature probes ENV-TEMP.
- ENV-TEMP
- This is just a temperature probe with no other capabilities.
- It is powered via PoE from the BASE-GATEWAY unit.
Proposal is
- to put 2 ENV-TEMP sensors (#1 and #2) along the Y-arm at the end and midway. These are powered and read through a BASE-GATEWAY (#A) at the vertex. The BASE-GATEWAY (#A) will serve as temperature sensor for the vertex.
- We put one ENV-TEMP(#3) at the X-end powered and read through by another BASE-GATEWAY (#B) at the midpoint of X-arm.
- Both BASE-GATEWAY are connected by ethernet cables to the network switch. That's it.
These sensors can be configured over network by going to their assigned IP addresses. I'm not sure at the moment how to configure the dB files to get them to write on slow EPICS channels.
We will have an unused port on the BASE-GATEWAY (#B) which can be used to run another temperature sensor, maybe at an important rack, PSL table or somewhere else.
In future, if more sensors are required, there are expansion (network switch like) options for BASE-GATEWAY or daisy-chain options for the probes.
Edit Fri Jun 18 16:28:13 2021 :
See this [wiki page](https://wiki-40m.ligo.caltech.edu/Physical_Environment_Monitoring/Thermometers) for updated plan and final quote. |
Attachment 1: 40mTempSensors.pdf
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16323
|
Mon Sep 13 17:05:04 2021 |
Tega | Summary | PEM | Infrasensing temperature sensor modbus configuration |
Anchal mentioned it would be good to put more details about how I arrived at the values needed to configure the modbus drive for the temperature sensor, since this information is not in the manual and is hard to find on the internet, so here is a breakdown.
So the generic format is:
drvAsynIPPortConfigure("<TCP_PORT_NAME>","<UNIT_IP_ADDRESS>:502",0,0,1)
modbusInterposeConfig("<TCP_PORT_NAME>",0,5000,0)
drvModbusAsynConfigure("<PORT_NAME>","<TCP_PORT_NAME>",<slaveAddress>,<modbusFunction>,<modbusStartAddress>,<modbusLength>,<dataType>,<pollMsec>,<plcType>)
which in our case become:
drvAsynIPPortConfigure("c1pemxendtemp","192.168.113.240:502",0,0,1)
modbusInterposeConfig("c1pemxendtemp",0,5000,0)
drvModbusAsynConfigure("C1PEMXENDTEMP","c1pemxendtemp",0,4,199,2,0,1000,"ServerCheck")
As can be seen, the parameters of the first two functions "drvAsynIPPortConfigure" and "modbusInterposeConfig" are straight forward, so we restrict our discussion to the case of third function "drvModbusAsynConfigure". Well, after hours of trolling the internet, I was able to piece together a coherent picture of what needs doing and I have summarised them in the table below.
drvModbusAsynConfigure
Once the asyn IP or serial port driver has been created, and the modbusInterpose driver has been configured, a modbus port driver is created with the following command:
drvModbusAsynConfigure(portName, # used by channel definitions in .db file to reference this unit)
tcpPortName, # reference to portName created with drvAsynIPPortConfigure command
slaveAddress, #
modbusFunction, #
modbusStartAddress, #
modbusLength, # length in dataType units
dataType, #
pollMsec, # how frequently to request a value in [ms]
plcType); #
drvModbusAsynConfigure command |
Parameter |
Data type |
Description |
portName |
string |
Name of the modbus port to be created.
|
tcpPortName |
string |
Name of the asyn IP or serial port previously created.
tcpPortName = { 192.168.113.240:502, 192.168.113.241:502, 192.168.113.242:502 }
|
slaveAddress |
int |
The address of the Modbus slave. This must match the configuration of the Modbus slave (PLC) for RTU and ASCII. For TCP the slave address is used for the "unit identifier", the last field in the MBAP header. The "unit identifier" is ignored by most PLCs, but may be required by some.
ServersCheck API ignores this value, as confirmed with pymodbus query, so set to default value:
slaveAddress = 0
|
modbusFunction |
int |
modbus supports the following 8 Modbus function codes:
Modbus Function Codes |
Access |
Function description |
Function code |
Bit access |
Read Coils |
1 |
Bit access |
Read Discrete Inputs |
2 |
Bit access |
Write Single Coil |
5 |
Bit access |
Write Multiple Coils |
15 |
16-bit word access |
Read Input Registers |
4 |
16-bit word access |
Read Holding Registers |
3 |
16-bit word access |
Write Single Register |
6 |
16-bit word access |
Write Multiple Registers |
16 |
|
modbusStartAddress |
int |
Start address for the Modbus data segment to be accessed.
(0-65535 decimal, 0-0177777 octal).
Modbus addresses are specified by a 16-bit integer address. The location of inputs and outputs within the 16-bit address space is not defined by the Modbus protocol, it is vendor-specific. Note that 16-bit Modbus addresses are commonly specified with an offset of 400001 (or 300001). This offset is not used by the modbus driver, it uses only the 16-bit address, not the offset.
For ServersCheck, the offset is "30001", so that
modbusStartAddress = 30200 - 30001 = 199
|
modbusLength |
int |
The length of the Modbus data segment to be accessed.
This is specified in bits for Modbus functions 1, 2, 5 and 15.
It is specified in 16-bit words for Modbus functions 3, 4, 6 and 16.
Length limit is 2000 for functions 1 and 2, 1968 for functions 5 and 15,
125 for functions 3 and 4, and 123 for functions 6 and 16.
ServersCheck uses two's complement 32-bits word (with big-endian byte order & little-endian word order) format to store floating-point data, as confirmed with pymodbus query, so that:
modbusLength = 2
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modbusDataType |
int |
The modbusDataType is used to tell the driver the format of the Modbus data. The driver uses this information to convert the number between EPICS and Modbus. Data is transferred to and from EPICS as epicsUInt32, epicsInt32, and epicsFloat64 numbers.
Modbus data type:
0 = binary, twos-complement format
1 = binary, sign and magnitude format
2 = BCD, unsigned
3 = BCD, signed
Some Modbus devices (including ServersCheck) use floating point numbers, typically by storing a 32-bit float in two consecutive 16-bit registers. This is not supported by the Modbus specification, which only supports 16-bit registers and single-bit data. The modbus driver does not directly support reading such values, because the word order and floating point format is not specified.
Note that if it is desired to transmit BCD numbers untranslated to EPICS over the asynInt32 interface, then data type 0 should be used, because no translation is done in this case.
For ServersCheck, we wish to transmit the untranslated data, so:
modbusDataType = 0
|
pollMsec |
int |
Polling delay time in msec for the polling thread for read functions.
For write functions, a non-zero value means that the Modbus data should
be read once when the port driver is first created.
ServersCheck recommends setting sensor polling interval between 1-5 seconds, so we can try:
pollMsec = 1000
|
plcType |
string |
Type of PLC (e.g. Koyo, Modicon, etc.).
This parameter is currently used only to print information in asynReport.
In the future it could be used to modify the driver behavior for a specific PLC.
plcType = "ServersCheck"
|
Useful links
https://nodus.ligo.caltech.edu:8081/40m/16214
https://nodus.ligo.caltech.edu:8081/40m/16269
https://nodus.ligo.caltech.edu:8081/40m/16270
https://nodus.ligo.caltech.edu:8081/40m/16274
http://manuals.serverscheck.com/InfraSensing_Sensors_Platform.pdf
http://manuals.serverscheck.com/InfraSensing_Modbus_manualv5.pdf
https://community.serverscheck.com/discussion/comment/7419#Comment_7419
https://wiki-40m.ligo.caltech.edu/CDS/SlowControls
https://www.slac.stanford.edu/grp/ssrl/spear/epics/site/modbus/modbusDoc.html#Creating_a_modbus_port_driver
https://github.com/riptideio/pymodbus
https://en.wikipedia.org/wiki/Modbus
https://deltamotion.com/support/webhelp/rmctools/Communications/Ethernet/Supported_Protocols/Ethernet_Modbus_TCP.htm |
16329
|
Tue Sep 14 17:19:38 2021 |
Paco | Summary | PEM | Excess seismic noise in 0.1 - 0.3 Hz band |
For the past couple of days the 0.1 to 0.3 Hz RMS seismic noise along BS-X has increased. Attachment 1 shows the hour trend in the last ~ 10 days. We'll keep monitoring it, but one thing to note is how uncorrelated it seems to be from other frequency bands. The vertical axis in the plot is in um / s |
Attachment 1: SEIS_2021-09-14_17-33-12.png
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16331
|
Tue Sep 14 19:12:03 2021 |
Koji | Summary | PEM | Excess seismic noise in 0.1 - 0.3 Hz band |
Looks like this increase is correlated for BS/EX/EY. So it is likely to be real.
Comparison between 9/15 (UTC) (Attachment 1) and 9/10 (UTC) (Attachment 2) |
Attachment 1: C1-ALL_393F21_SPECTRUM-1315699218-86400.png
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Attachment 2: C1-ALL_393F21_SPECTRUM-1315267218-86400.png
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16416
|
Wed Oct 20 11:16:21 2021 |
Anchal | Summary | PEM | Particle counter setup near BS Chamber |
I have placed a GT321 particle counter on top of the MC1/MC3 chamber next to the BS chamber. The serial cable is connected to c1psl computer on 1X2 using 2 usb extenders (blue in color) over the PSL enclosure and over the 1X1 rack.
The main serial communication script for this counter by Radhika is present in 40m/labutils/serial_com/gt321.py.
A 40m specific application script is present in the new git repo for 40m scripts, in 40m/scripts/PEM/particleCounter.py. Our plan is to slowly migrate the legacy scripts directory to this repo overtime. I've cloned this repo in the nfs shared directory at /opt/rtcds/caltech/c1/Git/40m/scripts which makes the scripts available at all computers and keep them upto date in all computers.
The particle counter script is running on c1psl through a systemd service, using service file 40m/scripts/PEM/particleCounter.service. Locally in c1psl, /etc/systemd/system/particleCounter.service is symbollically linked to the file in the file.
Following channels for particle counter needed to be created as I could not find any existing particle counter channels.
[C1:PEM-BS_PAR_CTS_0p3_UM]
[C1:PEM-BS_PAR_CTS_0p5_UM]
[C1:PEM-BS_PAR_CTS_1_UM]
[C1:PEM-BS_PAR_CTS_2_UM]
[C1:PEM-BS_PAR_CTS_5_UM]
These are created from 40m/softChansModbus/particleCountChans.db database file. Computer optimus is running a docker container to serve as EPICS server for such soft channels. To add or edit channels, one just need to add new database file or edit database files in thsi repo and on optimus do:
controls@optimus|~> sudo docker container restart softchansmodbus_SoftChans_1
softchansmodbus_SoftChans_1
that's it.
I've added the above channels to /opt/rtcds/caltech/c1/chans/daq/C0EDCU.ini to record them in framebuilder. Starting from 11:20 am Oct 20, 2021 PDT, the data on these channels is from BS chamber area. Currently the script is running continuosly, which means 0.3u particles are sampled every minute, 0.5u twice in 5 minutes and 1u, 2u, and 5u particles are sampled once in 5 minutes. We can reduce the sampling rate if this seems unncessary to us. |
Attachment 1: PXL_20211020_183728734.jpg
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16420
|
Thu Oct 21 11:41:31 2021 |
Anchal | Summary | PEM | Particle counter setup near BS Chamber |
The particle count channel names were changes yesterday to follow naming conventions used at the sites. Following are the new names:
C1:PEM-BS_DUST_300NM
C1:PEM-BS_DUST_500NM
C1:PEM-BS_DUST_1000NM
C1:PEM-BS_DUST_2000NM
C1:PEM-BS_DUST_5000NM
The legacy count channels are kept alive with C1:PEM-count_full copying C1:PEM-BS_DUST_1000NM channel and C1:PEM-count_half copying C1:PEM-BS_DUST_500NM channel.
Attachment one is the particle counter trend since 8:30 am morning today when the HVAC wokr started. Seems like there was some peak particle presence around 11 am. The particle counter even counted 8 counts of particles size above 5um!
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Attachment 1: ParticleCountData20211021.pdf
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16421
|
Thu Oct 21 15:22:35 2021 |
rana | Summary | PEM | Particle counter setup near BS Chamber |
SVG doesn't work in my browser(s). Can we use PDF as our standard for all graphics other than photos (PNG/JPG) ? |
16422
|
Thu Oct 21 15:24:35 2021 |
rana | Summary | PEM | Particle counter setup near BS Chamber |
rethinking what I said on Wednesday - its not a good idea to put the particle counter on a vac chamber with optics inside. The rumble from the air pump shows up in the acoustic noise of the interferometer. Let's look for a way to mount it near the BS chamber, but attached to something other than vacuum chambers and optical tables.
Quote: |
I have placed a GT321 particle counter on top of the MC1/MC3 chamber next to the BS chamber.
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16423
|
Fri Oct 22 17:35:08 2021 |
Ian MacMillan | Summary | PEM | Particle counter setup near BS Chamber |
I have done some reading about where would be the best place to put the particle counter. The ISO standard (14644-1:2015) for cleanrooms is one every 1000 m^2 so one for every 30m x 30m space. We should have the particle counter reasonably close to the open chamber and all the manufactures that I read about suggest a little more than 1 every 30x30m. We will have it much closer than this so it is nice to know that it should still get a good reading. They also suggest keeping it in the open and not tucked away which is a little obvious. I think the best spot is attached to the cable tray that is right above the door to the control room. This should put it out of the way and within about 5m of where we are working. I ordered some cables to route it over there last night so when they come in I can put it up there. |
16503
|
Mon Dec 13 15:05:47 2021 |
Tega | Update | PEM | git repo for temp sensor and sus medm |
[temperature sensor]
git repo: https://git.ligo.org/40m/tempsensor.git
todo
Update the temp sensor channels to fit with cds format, ie. "C1:PEM-TEMP_EX", "C1:PEM-TEMP_EY", "C1:PEM-TEMP_BS"
- Use FLOAT32_LE data format for the database file (/cvs/cds/caltech/target/c1pem1/tempsensor/C1PEMaux.db) to create the new channels.
- Keep the old datadase code and channels so we can compare with new temp channels afterwards. Also we need a 1-month overlap b4 deleting the old channels.
[sus medm screen]
git repo: https://git.ligo.org/40m/susmedmscreen.git
todo (from talk with Koji)
- Link stateword display to open "C1CDS_FE_STATUS.adl"
- Damp filter and Lock filter buttons should open a 3x1 filter screen so that the 6 filters are opened by 2 buttons compared to the old screen that has 3 buttons connected to 2X1 filter screen
- Make the LOCKIN signla modulation flow diagramlook more like the old 40m screen since that is a better layout
- Move load coefficient button to top of sus medm screen (beside stateword)
- The rectangular red outline around the oplev display is confusing and needs to be modified for clarity
- COMM tag block should not be 3D as this suggests it is a button. Make it flat and change tag name to indicate individual watchdog control as this better reflect its functionality. Rename current watchdog switch to watchdog master is it does what the 5 COMM switches do at once.
- Macro pass need to be better documented so that when we call the sus screens from locations other than sitemap, we should know what macro variables to pass in, like DCU_ID etc.
- Edit sitemap.adl to point only to the new screens. Then create a button on the new screen that points to the old screen. This way, we can still access the old screen without clogging sitemap.
- Move the new screen location to a subfolder of where the current sus screens reside, /opt/rtcds/userapps/trunk/sus/c1/medm/templates
- Rename the overview screen (SUS_CUST_HSSS_OVERVIEW.adl) to use the SUS_SINGLE nomenclature, i.e. SUS_SINGLE_OVERVIEW.adl
- Keep an eye of the cpu usage of c1pem as we add BLRMS block for other optics.
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16504
|
Tue Dec 14 11:33:29 2021 |
Tega | Update | PEM | git repo for temp sensor and sus medm |
[Temperature sensor]
Added new temp EPICs channels to database file (/cvs/cds/caltech/target/c1pem1/tempsensor/C1PEMaux.db)
Added new temp EPICs channels to slow channels ini file (/opt/rtcds/caltech/c1/chans/daq/C0EDCU.ini)
[SUS medm screen]
Moved new SUS screen to location : /opt/rtcds/userapps/trunk/sus/c1/medm/templates/NEW_SUS_SCREENS
Place button on the new screen to link to the old screen and replace old screens link on sitemap.
Fixed Load Coefficient button location issue
Fixed LOCKIN flow diagram issue
Fixed watchdog labelling issue
Linked STATE WORD block to FrontEnd STATUS screen
Replaced the 2x1 pit/yaw filter screens for LOCK and DAMP fliters with 3x1 LPY filter screen
*Need some more time to figure out the OPTLEV red indicator |
16750
|
Fri Apr 1 14:26:19 2022 |
Ian MacMillan | Summary | PEM | Particle counter setup near BS Chamber |
I mounted the particle counter over the BS chamber attached to the cable tray as seen in Attachment 1. The signal cable runs through an active 30ft cable to the 1x2 rack. the wire is labeled and runs properly through the cable tray. The particle counter is plugged in at the power strip attached near the cable tray. The power cord is also labeled.
I restarted the particle counter service in the c1psl computer in the /etc/systemd/system/ folder using the commands
sudo systemctl restart particleCounter
sudo systemctl status particleCounter
I cannged the usb hub assigned in the service file to ttyUSB0 which is what we saw the computer had named it.
Checking the channels from this elog show the same particle count as when testing with the buttons and checking the screen. It seems that the channels had been down but are now restarted. |
Attachment 1: IMG_1407.jpg
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16754
|
Sat Apr 2 15:46:13 2022 |
rana | Summary | PEM | Particle counter setup near BS Chamber |
nice - please update the particle counter page in the 40m wiki. Its probably years out of date.
Quote: |
I mounted the particle counter over the BS chamber attached to the cable tray as seen in Attachment 1. The signal cable runs through an active 30ft cable to the 1x2 rack. the wire is labeled and runs properly through the cable tray. The particle counter is plugged in at the power strip attached near the cable tray. The power cord is also labeled.
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16967
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Thu Jun 30 19:24:24 2022 |
rana | Summary | PEM | effect of nearby CES construction |
For the proposed construction in the NW corner of the CES building (near the 40m BS chamber), they did a simulated construction activity on Wednesday from 12-1.
In the attached image, you can see the effect as seen in our seismometers:

this image is calculated by the 40m summary pages codes that Tega has been shepherding back to life, luckily just in time for this test.
Since our local time PDT = UTC - 7 hours, 1900 UTC = noon local. So most of the disturbance happens from 1130-1200, presumably while they are setting up the heavy equipment. If you look in the summary pages for that day, you can also see the IM lost lock. Unclear if this was due to their work or if it was coincidence. Thoughts? |
17209
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Tue Oct 25 09:57:34 2022 |
Paco | Configuration | PEM | Auto Z on trillium interface board |
I pressed the Auto-Z(ero) button for ~ 3 seconds at ~9:55 local (pacific) time on the trillium interface on 1X5. |
17210
|
Tue Oct 25 13:55:37 2022 |
Koji | Configuration | PEM | Auto Z on trillium interface board |
This nicely brought the sensing signal back to ~zero. See attachment
Some basic info:
- BS Seismometer is T240 (Trillium)
- The interface unit is at 1X5 Slot 26. D1002694
- aLIGO Trillium 240 Interface Quick Start Guide T1000742
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Attachment 1: Screen_Shot_2022-10-25_at_13.56.46.png
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17213
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Tue Oct 25 22:01:53 2022 |
rana | Configuration | PEM | Auto Z on trillium interface board |
thanks, this seems to have recentered well.
It looks like it started to act funny at 0400 UTC on 10/24, so thats 9 PM on Sunday in the 40m. What was happening then?

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Attachment 1: Screen_Shot_2022-10-26_at_4.45.30_PM.png
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17427
|
Thu Jan 26 18:20:43 2023 |
Anchal | Update | PEM | HEPA Monitor setup using WFS BLRMS |
I implemented the BLRMS on WFS1/2_I_PIT/YAW outputs and using there value, a HEPA state can be defined. I've currently set it up to use average of 10-30 Hz noise on WFS signals low passed at 0.3 Hz. For ON threshold of 100 and OFF threshold of 50, it is working for my limited testing time. To read HEPA state, one can do caget C1:IOO_HEPA_STATE. I've turned OFF HEPA for tonight's shimmer test. This is bare bones quick attempt, people can make the screen more beautiful and add more complexity if required in future. |
Attachment 1: HEPA_MONITOR.png
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17429
|
Fri Jan 27 11:26:31 2023 |
rana | Update | PEM | HEPA Monitor setup using WFS BLRMS |
this is very exciting! Its the beginning of the task of reducing vast amounts of PEM data into human-useful (bite sized) info. Imagine if we had 60 Hz BLRMS on various channels - we would know exactly when ground loops were happening or disappearing. |
12
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Wed Oct 24 08:58:09 2007 |
steve | Other | PSL | laser headtemp is up |
C1:PSL-126MOPA_HTEMP is 19.3C
Half of the chiller's air intake was covered by loose paper |
Attachment 1: htempup.jpg
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15
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Thu Oct 25 22:02:58 2007 |
rob | Routine | PSL | HEPAs maxed |
In light of the SoCal fires, I turned the PSL HEPAs up to 100%. |
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Wed Nov 7 16:07:03 2007 |
steve | Update | PSL | PSL & IOO trend |
1.5 days of happy psl-ioo with litle bumps in C1:PSL-126MOPA_HTEMP |
Attachment 1: psl1.5dtrend.jpg
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Thu Nov 8 15:57:53 2007 |
tobin | Configuration | PSL | shelf removed |
I removed the sheet metal shelf from the PSL enclosure, for easier access to the ISS.
ISS investigations ongoing. |
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Thu Nov 8 18:44:01 2007 |
tobin | Configuration | PSL | ISS |
Tobin, Rob
With the Sense PD blocked, I adjusted the offset trim of the fourth stage in the ISS servo until the current shunt signal was zeroed. After this adjustment, we are able to crank the ISS gain all the way up to 30 dB without CS saturations (provided the HEPA is turned down to a very quiet level), getting about 35kHZ UGF at that gain setting. However, the current shunt mean value was still enormous.
Examining the current shunt signal on a fast scope, we saw an enormous (>2Vpp) 3.6 MHz sawtooth signal. Going up the chain of op-amps, we found that U1, as measured at the "Filter Out" testpoint, is oscillating wildly at 12 MHz (680 mVpp). |
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Fri Nov 9 09:37:55 2007 |
steve | Update | PSL | head temp hiccup |
Just an other PSL-126MOPA_HTEMP hiccup.
The water chiller is at 20.00C |
Attachment 1: headtempup.jpg
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Fri Nov 9 17:33:33 2007 |
rob | Configuration | PSL | ISS |
The 3.7 MHz is actually on the light. It's the beat between the 29.5 MHz sidebands and the 33.2 MHz sidebands. There are pads in the ISS PCB for a filter to notch this frequency--John is working on it.
I also found a 1.2 ND filter on the lens which focuses the beam on the ISS diodes. I replaced it with a 0.6 ND filter, which brought the ISS DC level (on the screen) up to ~4.2 (it saturates at 5). Once John finishes the filter we should be able to crank up the gain. |
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Fri Nov 9 21:36:14 2007 |
rob | Configuration | PSL | FSS |
rob, rana
We looked at the FSS a bit today. The most we could get out of it with the gain sliders was a UGF of around 95kHz. After a bit of tweaking the waveplate after the AOM, this got up to ~115kHz. We should be able to get at least 500kHz. This system needs a fair amount of work. |
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Mon Nov 12 15:05:49 2007 |
rob | Configuration | PSL | FSS |
Spent a bit of time fiddling with the FSS again today. In a not-particularly-systematic manner, I raised the input-side of the 21.5MHz PC, adjusted the half-wave plate in front of it, touched up the RC alignment and the alignment onto the transmitted and reflected diodes. This got us a ~15% increase in
transmitted light, and I was able to push the UGF to 140kHz with the common gain slider at 30dB and the FAST gain slider at 22dB. The next options include adjusting the AOM setup, mode matching into the RC, and just increasing the pickoff fraction right from the getgo. |
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Mon Nov 12 15:18:34 2007 |
rob | Update | PSL | ISS |
After John soldered a 3.7 MHz notch filter onto the ISS board, I took a quick TF and RIN measurement. The out-of-loop RIN is attached, including a dark noise trace, and with the gain slider at 10dB. The UGF is 35kHz with a phase margin of 30deg. John is currently doing a more thorough inspection, and will detail his findings in a subentry. |
Attachment 1: ISS.png
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Mon Nov 12 23:44:19 2007 |
John | Update | PSL | ISS |
Quote: |
After John soldered a 3.7 MHz notch filter onto the ISS board, I took a quick TF and RIN measurement. The out-of-loop RIN is attached, including a dark noise trace, and with the gain slider at 10dB. The UGF is 35kHz with a phase margin of 30deg. John is currently doing a more thorough inspection, and will detail his findings in a subentry. |
No progress on the ISS tonight. I tried to implement a new filter (attached)to try and gain some phase before the notch. If anything this made things worse. More work is needed.
The ISS loop is off and the power is off at the chassis. |
Attachment 1: ISSfilter.jpg
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Tue Nov 13 14:33:40 2007 |
John | Update | PSL | ISS filter |
The transfer function from 'In Loop Error Point Monitor' to TP3 the filter out test point on the ISS board.
-33dB at 3.715MHz. |
Attachment 1: PB130035.JPG
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Attachment 2: DSC_0165.JPG
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Wed Nov 14 12:47:19 2007 |
tobin | Update | PSL | ISS |
John, Tobin
With John's notch filter installed and the increased light on the ISS sensing diode, we were able to get a UGF of about 60 kHz with the gain slider set to about 20 dB. This morning we met with Stefan to learn his ISS-fu.
His recommendations for the ISS include:
- Replace the cables from the board to the front panel connectors if this hasn't already been done.
- Replace the input opamps with 4131's. Be sure to test both positive and negative input signals.
- Check that all the compensation capacitors are in place and are 68 pF
- Make sure all the feedback loops have high frequency rolloff
- The ISS board reads the PDs differentially; make sure the PD sends differentially.
- Add a big (ie 10uF tantalum) capacitor to the PD to suppress power supply noise
- Add bigger power supply bypass caps to the ISS
I just took sensing noise spectra (from the PD DC bnc ports) and then took the photodiodes off the table to check that they have the negative end of the differential line connected to ground. (I placed black metal beam blocks on the table in place of the ISS PD's. Also, from the ISS schematic, it looks like it sends a differential output to the PD DC bnc ports, but we have been plugging them directly into the SR785 (grounding the shield). We should make a little BNC-doodle that separates the signal+shield to go into the A and B inputs on the spectrum analyzer.) Opening up one of the photodiodes, it appears that the negative line of the differential output is not connected. Will continue later this afternoon. |
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Wed Nov 14 17:50:00 2007 |
tobin | Update | PSL | ISS |
Here's the current wiring between the ISS and its PDs:
pin | cable | PD | ISS |
1 | blue | +5 | +5 |
2 | red | +15 | +15 |
3 | white | -15 | -15 |
4 | brown | OUT | IN PD + |
5,6,7,8 | no connection | no connection | GND |
9 | black | GND | IN PD -
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The schematics for the ISS and the PDs are linked from our wiki.
We'll connect the ISS GND to the PD GND. |
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Thu Nov 15 04:18:11 2007 |
John | Summary | PSL | PMC cavity pole measurements |
In connection with our work on the ISS I attempted to measure the PMC cavity pole.
I swept the PMC PZT and looked at the transmission through the cavity on the ISS Monitor diode (which is now back on the table, feel free to remove it again tomorrow).
To avoid thermal effects I reduced the laser power using the half wave plate at the laser ouput (rotated from 6 deg to 340deg).
I swept the PZT using the triangle wave command "trianglewave C1: PSL-PMC_RAMP -3.5 3.3 20 200". I noticed that the functional form of the resonances deteriorated over the duration of the excitation. Each sweep was able to capture just over one FSR. The resonances were a little close to the 'points' of the triangle wave for my liking although I don't think PZT hysteresis was a big factor.
Looking at the data the peaks are not of uniform width across a sweep or between consecutive sweeps. Hence any results from this mesurement are not particularly useful. I can't be sure if this was due to misalignments, thermal effects, higher order mode content or some other affect.
Rob suggests sweeping the laser frequency using the NPRO PZT instead. |
Attachment 1: Peaks.jpg
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Tue Nov 20 10:11:33 2007 |
John | Summary | PSL | PMC pole measurements |
We measured the PMC pole in the following way.
1. Reduced laser power by rotating lambda/2 plate at laser output. Thermal effects in the PZT distort resonance peaks. Reducing power too much leads to problems with digitisation error.
2. Sweep NPRO PZT (C1: PSL-FSS_INOFFSET) using trianglewave. Record ramp, PMC transmission and reference cavity transmission ('C1: PSL-FSS_FAST','C1: PSL-ISS_INMONPD_F','C1: PSL-FSS_RCTRANSPD_F).
3. Since the PZT cannot sweep a full FSR in the PMC we looked at the sideband resonances within the reference cavity to calibrate the actuator.
Result: 7.35 +/- 0.22 MHz/V
4. Use #3 to calibrate the x axis of the PMC transmission.
5. Fit PMC resoances to an Airy function to get finesse. Take an average, weighted according to the resnorm. Calculate cavity pole frequency.
Result: 380kHz +/- 59kHz. This corresponds to a finesse of ~936. According to this plot the nominal pole is at 488kHz and the finesse is 732.
This is by no means a definitive measurement due to the misshapen resonance peaks recorded. |
Attachment 1: FittedPMCPeak.jpg
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Wed Nov 21 14:31:41 2007 |
rob | Update | PSL | FSS twiddle |
I `tweaked' the FSS path today. Here's what I did:
1) Shut down the FSS autolocker
2) Turn off FSS servo
3) Assume the beam coming back from the AOM is double-first-order, and don't make any changes large enough to lose it.
4) Tweak the alignment of these components to maximize the incident power on the RC reflected diode:
a) PBS before AOM
b) AOM
c) curved mirror after the AOM
5) Translate the AOM such that the beam moves away from the PZT, then when it levels off (no more power gains with movement),
move it back just a little bit so there's a teensy drop in power. This should but the beam as close to the edge as possible,
but whether or not it's the best place is still to be determined.
6) Lock the FSS, and align the mirrors into the frequency reference cavity.
After all this, the RC transmitted power went from .57 to .73 -- probably not a big enough change to account for the missing loop
gain, but we'll know more once the loop gets measured (after Alberto stops hogging the Agilent network analyzer).
Other possible routes include a systematic check of the upstream path (e.g., the Pockels cell) and just increasing the pickoff fraction for the FSS. |
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Tue Nov 27 15:45:08 2007 |
rob | Configuration | PSL | FSS loop |
It's unclear (to me, at least) what was the end result of the FSS path tweaking before Thanksgiving. Today I measured the open loop gain, and it was still around 100kHz, even with the gain sliders maxed out, but it looked really crappy with a sharp cutoff around the UGF. Then, on a lark, I pushed around the "Input Offset Adjust" slider, which sums an offset into the signal coming out of the mixer. By moving this slider to 7V, I got the UGF to 500kHz with 45 deg of phase. That would be fine, and we could go offset hunting, but the same thing happens if one puts in a large negative value! I don't really understand what's going on, but it seems like weirdness in the electronics. Unfortunately the web interface to the conlog is not running (presumably because the `new' linux1 doesn't have its apache server running) and my command line conlog efforts have been stymied. So, I don't know what the historical settings of this offset are, but zero is definitely not a good setting right now. Here's a snapshot:
FSS
UGF: 500kHz
CG : 24dB
FG : 19dB
input offset: 7V
Phase Adjust: 1.09V
Phase Button: 0
RF Amp Adjust: 7.38V
margins:
phase: 45 deg
gain: 8dB |
Attachment 1: FSSsmall.jpg
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Tue Nov 27 20:47:00 2007 |
tobin | Update | PSL | FSS |
Rana, Tobin
We looked at the RF PD signal to the FSS (siphoning off a signal via a minicircuits directional coupler) and also took an open loop transfer function of the FSS. In the transfer function we saw the step at 100 kHz (mentioned by Rob) as well as some peculiar behavior at high frequency. The high frequency behavior (with a coupling of ~ -20 dB) turns out to be bogus, as it is still present even with the beam blocked. Rearranging the cabling had no effect; the cause is apparently inside the FSS. The step at 100 kHz turns out to be a saturation effect, as it moved as we lowered the signal amplitude, disappearing as we approached -60 dBm. (Above the step, the measurement data is valid; below, bogus.)
Transfer functions will be attached to this entry.
Some things to check tomorrow: the RF signal to the PC, RF AM generation by the PC, LO drive level into the FSS, RF reflection from the PC, efficiency of FSS optical path, quality of RF cabling. |
Attachment 1: fss-tf0001.pdf
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Wed Nov 28 04:21:46 2007 |
rana | Update | PSL | FSS |
Quote: | Rana, Tobin
We looked at the RF PD signal to the FSS (siphoning off a signal via a minicircuits directional coupler) and also took an open loop transfer function of the FSS. In the transfer function we saw the step at 100 kHz (mentioned by Rob) as well as some peculiar behavior at high frequency. The high frequency behavior (with a coupling of ~ -20 dB) turns out to be bogus, as it is still present even with the beam blocked. Rearranging the cabling had no effect; the cause is apparently inside the FSS. The step at 100 kHz turns out to be a saturation effect, as it moved as we lowered the signal amplitude, disappearing as we approached -60 dBm. (Above the step, the measurement data is valid; below, bogus.)
Transfer functions will be attached to this entry.
Some things to check tomorrow: the RF signal to the PC, RF AM generation by the PC, LO drive level into the FSS, RF reflection from the PC, efficiency of FSS optical path, quality of RF cabling. |
I would also add to Tobin's entry that we believe what Rob was seeing was saturation.
With the bi-directional coupler in there, the RF signal into the FSS board clearly went UP if moved the offset slider away from zero.
With a scope looking at the IN2 testpoint, we can see that there's less than 2 mV offset at zero slider offset.
One tangential thing we noticed with the coupler is that, in lock, the amount of reflected RF is around the same as that going in to the mixer.
I have always wanted to look at this but have only had uni-directional couplers in the past. I think that the double balanced mixer is inherently
not a 50 Ohm device during the times where the diodes are being switched. IF that's the case we might do better in the future by having an RF
buffer on board just before the mixer to isolate the PD head from these reflections. |
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Wed Nov 28 17:41:34 2007 |
rob | Update | PSL | FSS again |
I investigated the FSS a bit more today. I looked at the signals coming out of the FSS frequency reference, and saw that both the LO and PC drive were distorted, non-symmetric waveforms. In addition, the LO path had a 3dB attenuator, meaning the mixer was starved. I placed mini-circuits SLP-30 filters in both paths, and now both are nice sine waves. I also took out the 3dB att. With this work, and the CG slider maxed out at 30, the FSS open loop gain (for real this time) goes up to ~250kHz. Still needs more investigation. |
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Wed Nov 28 19:44:18 2007 |
tobin | Update | PSL | HEPA |
I found the HEPA turned off completely. I turned it on. |