Basic Pump Throughput Concepts

What is Pump Throughput?

The manufacturer of a vacuum pump supplies a chart for each pump showing pumping speed (volume in unit time) vs pressure. The example, for a fictitious pump, shows the pumping speed is substantially constant over a large pressure range.

By multiplying pumping speed by pressure at which that pumping speed occurs, we get a measure called pump throughput. We can tabulate those results, as shown in the table below, or plot them as a graph of pressure vs pump throughput. As is clear from the chart,  pump throughput (which might also be called mass flow) decreases proportionally with PRESSURE, at least over the pressure range where pumping speed is constant.

The roughing pump speed actually will reach 0 l/s  at it's ultimate pressure performance.

Our roughing pump  pumping speed will slowly drop  as chamber pressure drops. Below 10 Torr this decrease is accelerated and bottoms out. This where the Root pump can help. See NASA evaluation of dry rough pumps...What is a root pump 

We have been operating succsessfully with a narrow margin. The danger is that the Maglev forline peaks at 4 Torr. This puts load on the small turbo TP2, TP3 &  large TP1

The temperature of these TP2 & 3  70 l/s drag turbos go up to 38 C and their  rotation speed slow to 45K rpm from 50K rpm because of the large volume 33,000 liters

Either high temp or low rotation speed of drag turbo or long time of overloading  can shut down the small turbo pumps......meaning: stop pumping, wait till they cool down

The manual gate valve installed helped to lower peak temp to 32C It just took too long.

We have been running with 2 external fans [one on TP1 & one on TP3]  for cooling and one aux drypump to help lowering the foreline pressure of TP2 & 3

The vacuum control upgrade should include adding root pump into the zero pumping speed range.

Atm1,   Pump speed chart:   TP1  turbo -red, root pump -blue and mechanical pump green. Note green color here representing an oily rotory pump. Our small drypumps [SH-100] typically run above 100 mTorr

                                           They are the forepump of TP2 & 3     Our pumpdown procedure: Oily Leybold rotory pumps ( with safety orifice 350 mT to atm ) rough to 500 mTorr

                                                                                                 Here we switch over to TP2 & 3 running at 50k RPM with drypumps SH-100 plus Aux Triscroll

                                                                                                 TP1- Maglev rotating full speed when V1 is opened at full volume at 500 mTorr 

                         History: the original design of the early 1990s had no dry scroll pumps. Oil free dry scrools replaced the oily forepumps of TP2 & TP3 in ~2002  at the cost of degrading the forline pressure somewhat.

                                     We had 2 temperature related Maglev failers in 2005 Aug 8 and 2006 April 5  Osaka advised us to use AUX fan to cool TP1  This helped. 

Atm2,   Wanted Root pump - Leybold EcoDry 65 plus  

Atm3,   Typical 8 hrs pumpdown from 2007 with TP2 & 3 

Atm4,   Last pumpdown zoomed in from 400 mT to 1mT with throttled gate  valve took 9 hrs  The foreline pressure of TP1 peaked at 290 mT, TP3 temperature peaked at 32C

            This technic is workable, but 9 hrs is too long.

Atm5,   The lowest pressure achived in  the 40m Vacuum Envelope 5e-7 Torr with pumps Maglev  ~300 l/s,  Cryo 1500 l/s  and 3 ion pumps of 500 l/s      [ in April 2002 at pumpdown 53 day 7 ] with annuloses at ~ 10 mTorr

Atm6,  Osaka TG390MCAB Throughput with screen ~300 L/s at 12 cfm backing pump

6.2M Bandon, OR did not trip any sus

Glitch, small amplitude, 350 counts  &  no trip.

The second big glich trips ETMX sus. There were small earth quakes around the glitches. It's damping recovered.

Small earth quakes and suspensions. Which one is the most free and most sensitive: ITMX

The rat is cut by mechanical trap and it was removed from ITMX south west location.

A nagy kover patkanyt a fogo elkapta es megolte.

All suspension tripped. Their damping restored. The MC is locked.

ITMX-UL & side magnets are stuck.

TP-1 Osaka maglev controller  [  model TCO10M,  ser V3F04J07 ]  needs maintenance. Alarm led  on indicating  that we need Lv2 service.

The turbo and the controller are in good working order.

*****************************

Hi Steve,

Our maintenance level 2 service price is $...... It consists of a complete disassembly of the controller for internal cleaning of all ICB’s, replacement of all main board capacitors, replacement of all internal cooling units, ROM battery replacement, re-assembly, and mandatory final testing to make sure it meets our factory specifications. Turnaround time is approximately 3 weeks.

  RMA 5686 has been assigned to Caltech’s returning TC010M controller. Attached please find our RMA forms. Complete and return them to us via email, along with your PO, prior to shipping the cont

Best regards,

Pedro Gutierrez

Osaka Vacuum USA, Inc.

510-770-0100 x 109

*************************************************

our TP-1 TG390MCAB is 9 years old. What is the life expectancy of this turbo?

                        The Osaka maglev turbopumps are designed with a 100,000 hours(or ~ 10 operating years) life span but as you know most of our end-users are

                        running their Osaka maglev turbopumps in excess of 10+, 15+ years continuously.     The 100,000 hours design value is based upon the AL material being rotated at

                        the given speed.   But the design fudge factor have somehow elongated the practical life span.  

We should have the cost of new maglev & controller in next year budget. I  put the quote into the wiki.

Electrician is coming to fix one of the fluorenent light fixture holder in the east arm tomorrow morning at 8am. He will be out by 9am.

The job did not get done. There was no scaffolding or ladder to reach troubled areas.

Yuki Miyazaki received 40m specific basic safety training.

M3.4 Colton shake did not trip sus.

Precondition: c1vac1 & c1vac2 all LED warning lights green [ atm3 ], the only error message is in the gauge readings NO COMM, dataviewer will plot zero [ atm1 ], valves are operational

When our vacuum gauges read " NO COMM " than our INTERLOCKS  do  NOT communicate either.

So V1 gate valve and PSL output shutter can not be triggered to close if the the IFO pressure goes up.                        

   [ only CC1_HORNET_PRESSURE reading is working in this condition because it goes to a different compuer ] 

Gautam and Steve,

Our TP3 drypump seal is at 360 mT [0.25A load on small turbo]  after one year.  We tried to swap in old spare drypump with new tip  seal. It was blowing it's fuse, so we could not do it.

Noisy aux drypump turned on and opened to TP3 foreline [ two drypumps are in  the foreline now ]  The pressure is 48 mT and 0.17A load on small turbo.

We want to measure the pressure gradient in the 40m IFO

Our old MKS cold cathodes are out of order. The existing working gauge at the pumpspool is InstruTech CCM501

The plan is to purchase 3 new gauges for ETMY, BS and MC2 location.

Basic cold cathode     or    Bayard-Alpert Pirani

Steve & Bob,

Bob removed the head cover from the housing to inspect the condition of the the tip seal. The tip seal was fine but the viton cover seal had a bad hump. This misaligned the tip seal and it did not allow it to rotate.

It was repositioned an carefully tithened. It worked. It's starting current transiant measured 28 A and operational mode 3.5 A

This load is normal with an old pump. See the brand new DIP7 drypump as spare was 25 A at start and  3.1 A in operational mode. It is amazing how much punishment a slow blow ceramic 10A  fuse can take [ 0215010.HXP ]

In the future one should measure the current pick up [ transient <100ms ] after the the seal change with Fluke 330 Series Current Clamp

It was swapped in and the foreline pressure dropped to 24 mTorr after 4 hours. It is very good. TP3 rotational drive current  0.15 A at 50K rpm   24C

The main laser went off when PSL doors were opened-closed. It was turned back on and the PSL is locked.

Gautam & Steve,

Our controller is back with Osaka maintenace completed. We swapped it in this morning.

Chub Osthelder received 40m specific basic safety traning today.

     It took at least ten years to rust away.

Physical plan is cleaning our roof and gutters today.

We have no coffee machine.

We are dreaming about it

We still do not have it.

The Contec test board with Dsub37Fs was on the top shelf of E7

I tried to plot a long trend MC Transmitted today. I could not get farther than 2017 Aug 4

The vacuum and MC are OK

It is posted at the 40m wiki with Gautam' help. Printed copies posted around doors also.

The 40m vacuum envelope has one large single O-ring on the OOC west side. All other doors have double O-ring with annuloses.

There are 3  spacers to protect o-ring. They should not be removed!

The Cryo-pump static seal to VC1 also viton. All gate valves and right angle valve plates have single viton o-ring seal.

Small single viton o-rings on all optical quality viewports.

Helium will permiate through these fast. Leak checking time is limited to 5-10 minutes.

All other seals are copper gaskits. We have 2 manual right angle with METAL-dynamic seal [ VATRING ] as  VV1 & RV1

Notes on the ion pumps and cryo pump:

• Our 4 ion pumps were closed off for a lomg time. I estmated their pressure to be around ~1 Torr. After talking with Koji we decided not to vent them.

• It'd be still useful to wire their position sensors. But make sure we do not actuate the valves. 

• The cryo pump was regenerated to 1e-4 Torr about 2 years ago. It's pressure can be ~ 2 Torr with charcoal powder. It is a dirty system at room temperature.

• Do not actuate VC1 and VC2, and keep its manual valve closed.

• IF someone feels we should vent them for some reason, let us know here in the elog before Monday morning.

Gautam, Aaron, Chub and Steve,

The vent 81 is completed.

4 ion pumps and cryo pump are at ~ 1-4 Torr (estimated as we have no gauges there), all other parts of the vacuum envelope are at atm. P2 & P3 gauges are out of order.

V1 and VM1 are in a locked state. We suspect this is because of some interlock logic.

TP1 and TP3 controllers are turned off.

Valve conditions as  shown: ready to be opened or closed or moved or rewired. To re-iterate: VC1, VC2, and the Ion Pump valves shouldn't be re-connected during the vac upgrade.

Thanks for all of your help.

Gautam, Aaron, Chub & Steve,

ETMY heavy door replaced by light one.

We did the following:  measured 950 particles/cf min of 0.5 micron at SP table, wiped crane and it's cable, wiped chamber,

                                placed heavy door on clean merostate covered stand, dry wiped o-rings and isopropanol wiped Aluminum light cover

Nothing tripped.

Chub & Steve,

We swapped in our  replacement of Varian V70D "bear-can" turbo as factory clean.

The new Agilent TwisTorr 84 FS  turbo pump [ model x3502-64002,  sn IT17346059 ]  with intake screen, fan, vent valve. The controller  [ model 3508-64001, sn IT1737C383 ] and a larger drypump IDP-7,  [ model x3807-64010, sn MY17170019 ] was installed.

Next things to do:

1. implement hardware interlock to close V4 at 80% pumping speed slowdown of "standby" rotation speed, estimated to be ~ 40,000 RPM ( when Standby 50K RPM  )
2. set up isolation valve in the foreline of TP2, with delayed start of the IDP-7 and/or use relay to power drypump.  This turbo controller can not switch off or start of the dry pump. [ Agilent isolation valve #X3202-60055, with position indicator, pneumatic actuation, 115V solenoid ]..........as a second thought, we do not need isolation valve if we go with the relay option. The IDP-7 has built in delay of 10-15 sec
3. test performance of new turbo

EQ did not trip anything. atm1

Just a REMINDER: our vacuum system is at atm to help the vacuum upgrade to Acromag.

Exceptions: cryo pump and 4 ion pumps

It is our first rainy day of the season..The roof is not leaking.

 Vac Status: The vac rack power was recycled yesterday and power to controller TP1,2 and 3 restored. atm3

                     VME is OFF.        Power to all other instrument are ON.       23.9Vdc 0.2A

ETMY sus tower with locked optic in HEPA tent at east end is standing by for action.

[Koji, Steve]

Summary

The N₂ pressure reading (C1:VAC-N2PRES) is now up-to-date after rebooting c1vac1.
The vaccum system is "Vacuum normal". We now have a space pressure transducer.

Introduction

Our vacuum valves are manipulated with 60~75 PSI of nitrogen. All the valves are configured to be closed in the case of low N₂ supply pressure.
In order to avoid this safety shutdown accidentally triggered, we have two N₂ cylinders to sustain the vacuum valves. When one cylinder goes to low
the mechanical valve switches over to the other cylinder.

We have the monitor channel for this (combined) cylinder pressure. One shoulbe be able to see periodical pressure variation when the auto cylinder
switch is operating. However, the nirogen pressure reading got stuck at 66 PSI on Dec.16, 2014 (See attached 60-day plot of N2 supply pressure). 

What we did

This morning we tracked down the cause of the trouble. We first closed the valves on EPICS and started to vary the N2 pressure.

Our first guess was the pressure transducer (Omega #236PC100GW) that was already 15 yrs old. We even has a sensor spare for replacement.
But it turned out that the direct voltage reading (to be 1mV/PSI) is changing correctly. The second guess was Omega Controller-Monitor
#DPiS32-C24 that is reading the voltage from the tranceducer. The display on this small black unit was changing corresponding to the
pressure change.

So our thought was
1) RS232C of the monitor unit is not working correctly
or
2) c1vac1 is not communicating with the monitor unit.

We wondered what could cause c1vac1 not communicating with the monitor unit, but we were afraid that some function got stuck
during either the nodus upgrade or chiara rebooting (or something else). So we decided to reboot c1vac1

In order to avoid any glitch in the main vacuum pressure, Steve disconnected some of the controller connectors for the closed valves.
We did this treatment before and it was successful.

Then c1vac1 was rebooted just by telnet and type reboot in the terminal.
Once the target is back in action, we noticed that the monitor value started to move.

Steve reverted the cables to the valves and operated the valves to recover "Vacuum Normal" state. Everything is now nicely settled.

1)Power to the seismometers were turned down,

2)Guralp2 was moved to North side of POX table

3)Guralp2 was aligned in N-s Direction and leveled before connecting

4)Power to seismometers was turned on once Guralp2 was connected

An exercise of optimally subtracting one seismometer signal by another using weiner filters was done. Results have been summarized document attached.

I used MC_L signal from the Mode Cleaner as the desired signal with GUR2_X as witness signals. I observed good subtraction where coherence is high. But there was noise added in other frequency bands. I am not sure how to avoid that.

Please find attached documents that contains relevant plots.

Steve measured an apparent power drop in the 2W NPRO output from 2.1W to 1.6W(elog entry no 3698) at 2.1A of diode current in the laser (elog entry:  2822).  It was later noticed that the laser temperature was set to about 45 degC while the initial calibration was done at 25 deg C.  

It was felt that the recent power drop may have something to do with the increase in the operating temperature of the laser from 25 to 45 deg C.  Therefore the laser was returned to 25 deg C and the power output was remeasured and found to be 2.1W as it was at the begining(elog entry:3709)

It was also noticed that returning the laser to 25 deg. C resulted in a loss of efficiency in coupling to the PMC.  We suspected that this might be due to multimode operating conditions in the laser at particular operating temperatures.  In order to see if this is indeed the case the laser power output was observed as a function of temperature.  We do notice a characteristic saw-tooth shape which might indicate multimode operation between 39 and 43 deg C.  It is best to verify this by observing the power fluctuations in the transmitted beam of the stabilised reference cavity.

The measurement was made by attenuating the roughly 2W laser beam by a stack of two Neutral Density filfers and then measuring the transmitted light with the PDA36A photodetector.  This was because both the power meters used in the past were found to have linear drifts in excess of 30% and fluctuations at the 10% level. 

  The power meter used in the measurements of elog entries 2822, 3698 and 3709 was the Ophir PD300-3W.  This power head has several damaged patches  and a slight movement of the laser spot changes the reading considerably.  To verify I checked the power out with another power meter (the Vector S310) and found that there is no significant variation of the power output with the temperature of the laser.  And the power at 2.1A of diode current is 2W with 10% fluctuation arising from slight repositioning of the laser head.  There are regions of the Ophir PD300 which show the laser power to be about 1.9W.

Thanh and I re-glued the magnet to the PRM following the procedure outlined by Jenne

The PRM in the gluing fixture has been placed in the little foil house and left to cure for a day.

If all goes well the balancing the PRM will be done tomorrow.

The mirror which was moved during the mode matching of PSL light to the MC (ref elog #3791) has been repositioned.  We once again have the green light from the NPRO on the X (south) arm available on the PSL table. 

This light was supposed to be collimated by the two plano convex lenses (f=200mm and f=50mm  ref to elog #3771) but it was converging.  So I moved the f=50mm lens backwards to make the beam collimated.  I checked the beam collimation by introducing an Al coated mirror infront of th PD and diverting the beam temporarily in a free direction.  I could then check the collinearity and collimation of both the green beams over a meter.  After alignment the mirror was removed and the light is now incident on the PD once again.  We can now proceed to look for green beats.

The power from the PSL NPRO was attenuated for the MC locking work of yesterday.  It has now been increased to the maximum by rotating the Half Wave Plate (HWP).  The power after the PSL is now about 450mW  (500mW - 10% picked off for the doubling).

The laser power was attenuated to 40 mW yesterday for ensuring that the power built up within the MC does not damage the optics. 

This however stopped us from the doubling work and besides also reduced the power available for locking the PMC. 

Therefore, today the laser attenuation was removed and once again 500mW is available at the exit of the PMC .  

However the power sent to the MC has been reduced to 60mW by changing one of the mirrors in the zig-zag to a 33% beam splitter.  Though about 450mW is incident on the beam splitter the reflected beam is only about 55mW since the mirror reflectance is specified for P polarised light incident at 45deg while ours is S-polarised incident at less than 45deg.   The light transmitted through the beam splitter has been blocked by a beam dump.

Yuta and Suresh

The MC2 transmission is seen on the QPD

Once the laser was locked to the cavity, and the PMC was able to follow the laser (ref: elogs by Yuta and Rana today)  we had a steady TEMoo mode in the MC.  This gave us sufficient transmission through MC2 to be easily visible with an IR viewer and we were able to guide the beam on to the QPD.  The beam however seemed to over fill the QPD, a lens (f=180mm) was placed before the beam folding mirror and the spot sized reduced.   The the QPD was found to be not fixed to the table and this was also recitified.  The signal level is still low: total signal is just about 7 DAQ steps amounting to about 5mV.  Tomorrow we plan to work on the alignment of the PSL and MC and thus increase this signal.

A new channel to observe the length variations in the MC.

A long BNC cable was laid from the MC locking electronics next (southwards) to the PSL table to the DAQ cards picking up the signals from the PRM OSEMS.  This is to pick up one of the MC locking signals and collect it on a DAQ channel.  However as there are no spare DAQ channels currently available one of the PRM OSEM (UL and LL) photodiode channels was unplugged and replaced with the signal from the long BNC cable.   For identifying the correct DAQ channel we put in a 2 Vpp 10Hz signal with a function generator into this BNC.  Tow signals can be picked up in this fashion and they are available on PRM_LLSEN_IN1 and PRM_ULSEN_IN1. We plan to use this for improving the alignment of the MC tomorrow. 

The algorithm for this alignment is that if the beam from the PSL is not centered on the MC1 then tilting MC1 would result in a change in the length of the cavity as seen by the light.  Using this as feedback the spot could be precisely centered on the MC1 and then the MC alignment could be completed by moving MC2 and MC3 to reobtain TEM_oo within the cavity.

Fiber coupling 1064 nm light at the end of X arm

This is 'work in progress'.  The attempt is to bring a few milliwatts of the 1064 nm light from the NPRO at the end of the South(X) Arm to the PSL table through an single mode optical fiber.  This would enable us to tune the two NPRO's to be less than 15 MHz apart by looking at their beat frequency before doubling.  Because we have a 1GHz bandwidth PD at 1064 nm, while the photodiode for green has a BW of about 30MHz.

A PBS (P-type) cube has been introduced into the beam of the X arm NPRO  (between the lamda/2 plate and the input lens of the doubling crystal).  By rotating the face of the PBS slightly away from normal incidence, I have diverted away 1.5mW of the 1064 light for coupling into the fiber. The beam has shifted slightly because of this and the green beam from the south arm has to be realigned to reach the PSL table.

A single mode fiber (Thorlabs SM980-5.8-125),  which was already laid half way, has been extended all the way to the PSL table. It runs along the  South arm in the cable tray. 

A pair of mirrors have been arranged in a zig-zag to steer the beam into a fiber coupler.  There was some hope that this coupler had been aligned at some point in the past and that attaching a fiber might result in some transmission.  But this is not the case and fiber coupler needs to be readjusted.

In order to see the light transmitted through the fiber, a camera has been set up on the PSL table.  Its output has been routed into the 'Ref Cavity reflected' video signal.  A video cable running from the ETMX to the Video-MUX used to be connected to the input channel 9 of the Video MUX.  This has now been shifted to output channel 25 of the MUX and disconnected from the camera at the ETMX.   The 'Ref Cav Refl.' video signal has been routed to the output channel 25.  The camera looking at the fiber output can now be seen on a local monitor at the end of the X arm and on the video monitor in the control room.

With the fiber disconnected, the 1064 nm beam was steered into the fiber coupler and its transmission maximised by observing  with an IR viewer.  The fiber was then connected and then the transmission at the PSL table was sought.  There was no transmission seen after a searching around this region for a few mins.

The plan is to purchase a Visual fault locator which would enable us to quickly get a rough alignment of the fiber coupler. A local vendor is listed as a distributor for this product from JDSU.  Contact info:

DuVac Electronics (EDGE)
Tel: 626-796-3291
Email: jack@duvac.com
1759 E Colorado Blvd
Pasadena, CA 91106

[Kiwamu, Suresh]

We decided to use the 1064nm beam reflected from the Y1-1037-45-P mirror after the collimation lens following the doubling crystal for coupling into the optical fiber (ref 3843 and 3847 ).

We replaced a beam dump which was blocking this beam with a Y1-1037-45-P mirror and directed the beam into the fiber coupler with another Y1-1037-45-P.  The power in this beam was about 1W.  This has been stepped down to 10mW by introducing a reflective ND filter of OD=2.  The reflected power has been dumped into a blade-stack beam dump.

Steve has ordered the The Visual Fault Locator from Fluke.  It is expected to arrive within a day or two.

The Fluke Visual Fault locator (Visifault) arrived and I used it to couple 1064nm light into the single mode fibre at the south-end-table.

Procedure used:

When the output end of the fiber is plugged into the Visifault the light emerges from at the south end (input side for 1064nm).  This light is collimated with the fiber coupler at that end and serves as a reference for the optical axis along which the 1064 light must be directed.  Once the two beams (red and 1064) are overlapped with the beam steering mirrors, the Visifault was disconnected from the fiber and the  fibre output ( 1064 at the PSL table) is maximized by walking the beam at the input end and adjusting the collimation at the input.

The output of the fiber has been collimated with a fiber coupler.

7.5mW are incident on the input end and 1.3mW have been measured at the output.    This output power is adequate for the observing the beats with PSL NPRO.