Charles Blakemore  our new undergrad help received 40m specific safety training today.

Cameras must be immediately anchord to avoid a possible collusion with the view port !

The fire department weighted and pressure checked our units today. Surprisingly they found one powder filled can. We can only use HALON  gas in the lab.

Evan got 40m specific safety training today.

Did someone unlock the back door by the (unofficial) bike storage lately?  Out of habit, I checked the door behind me while about to leave, and it is unlocked. 

Please recall that if you leave through that door, it should automatically lock behind you (if it was locked already), however if you unlock and enter through the back door, it stays unlocked until someone locks it again.

(Obviously, I'm locking the door before I actually go).

                                                 Recommended correction list:

1,  refill- upgrade first aid boxes

2,  maintain 18" ceiling to bookshelf clearance so the ceiling fire sprinklers are not blocked: room 101

3,  label chilled water supply & return valves in IFO room

4,  calibrate bake room hoods annually

5,  update safety sign at fenced storage

              40m still to do list:

1,   clean and measure all safety glasses

2,   annual crane inspection is scheduled for 8am March 19, 1013

3,   make PSL encloser shelf earthquake proof

Do you see something that is not safe? Add it to this list please.

Chloe Ling, Max Horton and Annalisa Allocca have received basic 40m specific safety training.

 All safety glasses were cleaned in soapy water by Bob. I measured their transmission at 1064 nm, 150 mW,  beam diameter 1.5 mm  They are in working order, no transmission.

 Inventory:

10 pieces of KG-5, fit over, from Laser Safety

 4 pieces of KG-5, std size, from Drever Lab, best visibility

 1 piece of KG-5 coated for visible, std size, from Kentek

15 pieces of green-plastic LOTG-YAG, fit over, from UVEX

 7 pieces of green-plastic B-D+S 137, std areo fit, from Sperian

 3 pieces of green-plastic, old Thorlab, fit over

 2 pieces of green-plastic, fit over, from Laservision

 8 pieces of braun- plastic, fit over, for green & IR protection, from UVEX & Thorlabs

Professional crane inspector: Fred Goodbar found two small leaks at the Vertex trolley as he was conducting the annual inspection of the 40m cranes.  Otherwise the cranes are in safe condition.

PDA255 at the MC transmission end is missing and whoever had removed it earlier has left the beam undamped.

It could be less than a mW beam...but it is still not acceptable to leave it that way.

On the other note, I have cleared up the unwanted optics from the same table.

 Albert, our new undergrad work force received 40m specific- basic safety training last week. Please read and sign 40m procedures booklet.

Let's see if the ripples observed in the MC ringdown can be due to tilt motion of the mirrors.

The time it takes to produce a phase shift corresponding to N multiples of 2*pi is given by:

t = sqrt(2*N*lambda/(L*omega_T^2*(alpha_1+alpha_2)))

L is the length of the MC (something like 13m), and alpha_1, alpha_2 are the DC tilt angles of the two mirrors "shooting into the long arms of the MC" produced by the MC control with respect to the mechanical equilibrium position. omega_T is the tilt eigenfrequency of the three mirrors (assumed to be identical). lambda = 1.064e-6m;

The time it takes from N=1 to N=2 (the first observable ripple) is given by: tau1 = 0.6/omega_T*sqrt(lambda/L/(alpha_1+alpha_2))

The time it takes from N=2 to N=3 is given by: tau2 = 0.77*tau1

etc

First, we also see in the measurement that later ripples are shorter than early ripples consistent with some accelerated effect. The predicted ripple durations tau seem to be a bit too high though. The measurements show something like a first 14us and a late 8us ripple. It depends somewhat on the initial tilt angles that I don't know really.

In any case, the short ripple times could also be explained if the tilt motions start a little earlier than the ringdown, or the tilt motion starts with some small initial velocity. The next step will be to program a little ringdown simulation that includes mirror tilts and see what kind of tilt motion would produce the ripples exactly as we observe them (or maybe tilt motion cannot produce ripples as observed).

Isn't it just a ringing of the intracavity power as you shifted the laser frequency abruptly?

Hmm. I don't know what ringing really is. Ok, let's assume it has to do with the pump... I don't see how the pump laser could produce these ripples. They have large amplitudes and so I always suspected something happening to the intracavity field. Therefore I was looking for effects that would change resonance conditions of the intracavity field during ringdown. Tilt motion seemed to be one explanation to me, but it may be a bit too slow (not sure yet). Longitudinal mirror motion is certainly too slow. What else could there be?

Laser frequency shift = longitudinal motion of the mirrors

Ringing: http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-20-24-2463

Ok, so the whole idea that mirror motion can explain the ripples is nonsense. At least, when you think off the ringdown with "pump off". The phase shifts that I tried to estimate from longitudinal and tilt mirror motion are defined against a non-existing reference. So I guess that I have to click on the link that Koji posted...

Just to mention, for the tilt phase shift (yes, there is one, but the exact expression has two more factors in the equation I posted), it does not matter, which mirror tilts. So even for a lower bound on the ripple time, my equation was incorrect. It should have the sum over all three initial tilt angles not only the two "shooting into the long arms" of the MC.

It is essential we take a look at the ringdown data for all measurements made so far to figure out what must be done to track the source of these notorious ripples. I've attached the plot for the same showing the decay time to be the same in all cases. About the ripples; it seems unlikely to both Jan and me that the ripples are some electronic noise because the ripples do not follow any common pattern or time constant. We have discussed with Koji about monitoring the frequency shift, the input power to the MC and also try other methods of shutting down the pump to track their source as the next steps.

 The measured power levels of the RF source harmonics are given below:

We are considering inclusion of bandpass filters centered on 11 and 55 MHz  to suppress the harmonics and meet the requirements specified in Alberto's thesis (page 88).

As part of the RF system upgrade some of the demod boards in the lab were modfied.  The filter U5 (see the circuit schematic) was replaced. These changes are tabulated below.

Next, I and Q phase has to be checked for orthogonality. And noise levels of the cards have to measured.

I am a little concerned about using these low pass filters so close to the band edge. Recall that there is no on-board preamp for the RF input to the mixer.

So, if the input impedance of the filters is not 50 Ohms, we will get some unwanted reflections and sensitivity to cable length.

I think its worth while to check the impedance or S-parameters of these things with the LO activated to find out if we need to remove them or not.

We found a stray unused heliax cable running from the LSC rack 1Y2 to a point between the cabinets 1X3 and 1X4. This cable will need to be redirected to the AS table in the new scheme.   It is labled C1LSC-PD5  The current situation has been updated as seen in the layout below

The suggested layout of the 1Y2 Rack is shown below.

To simplify the wiring, I have largely kept demod boards with the same same LO frequency close to each other. 

The Heliax cables land on the top and bottom of the of subracks.  These are currently flexible plastic sheets.  Steve has agreed to replace them with something more rigid.  It would be good to have eight N-type connectors on the top and eight  at the bottom.  As  demod boards occur in sets of eight per subrack.  So it would be convenient if the 11 and 55 Mhz Heliax cables land on the top and the rest at the bottom.  In the layout I have shown the current situation. 

The LO signals to the boards come from the RF Distribution box and this is kept in the middle so that cables to both the subracks can be kept short.

The outputs of the AA filter boards from both subracks  have to be connected to the SCSI Interface board with a twisted pair ribbon cable. 

New right angle PVC, 2 x 2 x  1/4" installed at the AP table to strain relief the 1/4" spiral corrugated RF coaxes.

As seen in the previous measurement the first harmonic of both the 11 MHz and 55 MHz outputs are about 30dB
higher than desired.  In an attempt to attenuate these and higher harmonics I introduced SBP-10.7 filters into
the 11MHz outputs and SLP-50 filters into the 55 MHz outputs.
Then I measured the height of the harmonics again and found that they were suppressed as expected.  Now harmonic
at 22 MHz is 58dB lower than the 11 MHz fundamental.  And the 110 MHz is lower by 55 dB compared to the 55 MHz
fundamental.  None of the higher harmonics are seen => they are below 70dB

SLP-50 has an insertion loss(IL) of 4.65 dB and Return Loss(RL) of 3dB.  It would be better to use SBP-60
(IL=1.4 dB and RL=23dB)

The filter on the 11 MHz lines is okay. The SBP-10.7 has IL=0.6 dB and RL=23 dB.

RF Amp operating temperature

Earlier measurement reported by Alberto in LIGO-T10004-61-v1 based on the LM34 temperature sensor were lower than that shown by placing a calibrated thermocouple sensor directly on the heat sink by about 5deg C. The difference probably arose because the LM34 was located on a separate free-hanging copper sheet attached to the RF Amp by a single screw, resulting in a gradient across the copper strip.   I tried to move the LM34 which was glued down, but broke the leads in the process.  I then replaced it with another one mounted much closer to the heat sink and held it down with a copper-strip clamp.  There is no glue involved and there is heatsink compound between the flat surface of the LM34 and the heatsink.  Picture attached. 

  The picture also shows the new filters which have been put in place to reduce the harmonics.  Note that the SBP-10.7 which was to go on the 11 MHz Demod output is located much farther upsteam due to space constraints.

RF Source box has been mounted in the 1X2 rack. 

Heliax cables have been directly attached to the box and anchored on the side of the 1X2 rack.  Here is a list of Helix cables which have been connected so far.

RF Distribution box has been mounted in the 1Y2 rack and is ready for use.

The box receives 11 and 55 MHz Demod Signals from the RF source located in the 1X2 rack.

[Joe, Jamie, Suresh]

We have installed the IDE to SCSI adaptor module into the 1X2 rack and have connected the AA filter outputs to it.

We have removed the following cables running between the 1X2 and 1X3 racks.

The long twisted pair ribbon cable which previously carried the ADC signals.

1X2-ASC 6, 1X2-ASC 47, 1X2-ASC 9, 1X2-ASC 8, 1X2-ASC 10, 1X2-ASC 7,

CAB-1X2-LSC 42, CAB 1X2-LSC 56,  CAB 1X2-LSC 41, CAB 1X2-LSC 43

1X3-2 ASC 47

We have also removed the following by mistake.  We will put them back them on Monday

1X2-LSC 21, 1X2-LSC-20.

We have also removed the ASC QPD cables and moved the QPD cards which were present in the middle Eurocate (#2) to the unused Eurocrate at the bottom position (#3).

The binary input cables at the back of the cards require to be supported so that their weight does not pull them out of the sockets at the back of the crates.

Some of the slots where we plan to plug in Demod boards (the 165 MHz boards)  are not currently connected to any binary output on the C1:LSC computer.  We need these binary controls for the fitlter modules on the cards.

When we eventually begin to use the 15PDs as planned, then we will occupy 30 ADC channels (I & Q outputs).  Currently we have just one ADC card installed on the C1:LSC providing 32 ADC channels.  Joe found another 16bit 32 channel ADC card in his stash but we need to get a timing+adaptor board for it. In general we are going to need the third Eurocrate.

A platform for the power supply of the RF Distribution box needs to be built and the power supply needs to be moved into the 1X2 rack rather than sit on top of 1X2 rack.

REFL55 has been installed on the AP table.  REFL11 has been moved to make space for a 50% beam splitter. The reflected beam from this splitter is about 30% of the transmitted beam power.  The reflected beam goes to REFL11 in the current configuration.  The DC levels are 1.2V on REFL 11 and 3.5V on the REFL55.

I redid some of the cabling on the table because the we need to choose the heliax cables such that they end up close to the demod board location.  As per the 1Y2 (LSC) rack layout given here, some of the PD signals have to arrive at the top and others at the bottom of the LSC rack.

Currently the PDs are connected as follows:

REFL11 PD --> Heliax (ASDD133) (arriving at the top of LSC rack) --> REFL11 Demod Board 

REFL55 PD --> Heliax (REFL166) (arriving at the top of LSC rack) --> AS55 Demod Board

AS55 PD --> Heliax (AS166) (arriving at the top of the LSC rack) --> not connected.

We are waiting for the Minicircuits parts to modify the rest of the demod boards.

The heliax cables arriving at the LSC rack are not yet fixed properly.  I hope to get this done with Steve's help today.

New right angle PVC front panel with SMA bulkhead connectors are in place. The connections are still lose. It is ready for Suresh to finalise his vision on it.

We now have the DC signal from three PDs available in the ADC channels 14,15 and 16.  The signals are from  REFL55, AS55 and POY photodiodes respectively.  As the DC signals on all the other PDs of the same port (REFL, AS and PO)  have the same information we do not need to monitor more than one DC PD at each port.

The LSC PD Interface Card, D990543 - Rev B, can take 4 PDs and provides the DC signals of the PDs on the connector P2 (the lower of the two) on the back plane of the chassis. An adaptor card, D010005-00, plugs into the back plane from the rear of the Eurorack and provides the four DC signals on two-pin lemo sockets.

I have connected the three DC signals from the relevant RF PDs (above) to a DC whitening filter, D990694-B-1 which is associated with the channels 9 to 16 of the ADC card.

The cables are in a bit of a mess right now as some of the PD power supply lines are too short to reach up the the Interface card in the top Eurocart. Steve and I plan to redo some of the cabling later today

The SLP-50 filters which were on the 55 MHz lines have been replaced with the SBP-60.  Their respective characteristics are given below:

SBP-60 has lower insertion loss and higher return loss.  

This may however change the phase of I and Q in the demod boards and they will therefore need to be readjusted.  Currently the output power level of 55 MHz demod is at 2dBm, whereas it ought to be at 6dBm.   I have not yet corrected that.  Once that is completed Kiwamu will adjust the phases.

 I shifted the temperature sensor to a new location.  See the photograph below.  I noticed that the higher temperature is reached on the side where there are two RF Amps.  So it would be better to check the temperature of that  area and make sure that it remains well below 65 deg.  The operating maxium is 65deg C

Here is a picture of the new RF source layout.

And here is a photograph of it

[Steve, Suresh]

We started to clean up the RF cables (heliax and PD interface cables)  at the LSC rack.

We have pulled out all the RF cables from the small hole on the side-board close to floor.  Passing the cables through this hole makes some of the cables much too short for good strain relief.  So we removed the side panel on the vacuum tube side and are going to pass the cables into the rack from there at about waist height.  We now have plenty of cable lengths to tie them off to the rack at several points.

We have traced all the available Heliax cables and have attached blank tags to them.  We have allocated some cables to REFL11, REFL55 and AS55.  These are therefore back in working order.  We have also taken stock of the available PD interface cables.  They do not have consistent names on both ends of the cable and we will identify and label the ends tomorrow.

MC is locked.  The auto-locker works fine.

Handing over the system for night time interferometer work now.  Will continue with the cabling tomorrow.

Today after Steve and I finished the RF cabling work for the day, Kiwamu noticed that there were no RF signals to be seen.  The problem was traced to disconnected 11 and 55 MHz Demod lines from the RF source.  But reconnecting them did not restore the signals.  It turned out that one of the Heliax cables had a loose N-type connector at its end and it finally came off while we were tightening it into place.

We replaced the damaged heliax with another (we have two spare running from 1X2 IOO rack to the 1Y2 LSC rack.  The new cable is used to be the LO 33.  It seems to have a 1.5dB loss.  Have to check this again tomorrow.

In the mean time I noticed that the power output of the 55MHz Demod port of the source was less than about -12dB. So I opened the source to take a look and found that all the voltage stabilisers were supplying 15V.  Even those which were supposed to be supplying 24V.  This was traced to a mistake in wiring the external power supply.  The wires had been labeled wrongly and as a result the 18V input line was connected to 28V source and vice versa.

After fixing this problem I reassembled the source checked the power output on all the ports and found everything was functioning as expected.  However after installation once again the unit failed.  The blue light on the power supply was not lighting up when switched on.  Suspecting a power supply problem I opened the unit again and found that a weak solder joint on one of the RF amplifiers had come loose and had overloaded one of the 24V stabilisers.   We, found a spare and replaced it.  The unit has been reassembled and is functioning fine.  The output power levels are

11MHz Demod -- 6dBm

55MHz Demod -- 5.5 dBm

11MHz EOM --   24dBm

55MHz EOM -- 28dBm

The Marconi is serving as the 11MHz source.  The Wenzel 11MHz source is giving 13.3 dBm and is okay.  But it needs to be checked for its performance as it may have been exposed to higher than rated power supply levels.

The 29.5MHz source is giving 7dBm.  It is supposed to be giving 13dBm. 

The Laboratory DC power supplies currently used for both the RF source and Distribution boxes need to be replaced with rack mounted Sorensen power supplies available in the lab.

[Jamie, Koji, Suresh]

We replaced splitters in several demod boards as per the table given below:

While doing a rough check of the boards I noticed that the REFL11 demod board had no signal on the Q output.

Rana also advised that we must use the boards which have the piggy-back amplifiers on those signals which are most useful.  We referred to Alberto's thesis and chose POY55 (MICH and SRCL), REFL11(PRCL)  and AS55 (DARM) as the most useful signals.  We currently have these amps on AS11, REFL11 and AS55.  We need to convert either AS11 or REFL11 into a POY55.  Since we need to troubleshoot REFL11, I thought we might as well modify that and in the process also fix its Q output.  So I renamed AS11 as REFL11 and will convert the old REFL11 into POY55 tomorrow.

Power splitter of different types have different pin-outs.  The way we mount a splitter depends on which type we are using.   I will detail the mounting scheme in a separate elog tomorrow.

 I think we should leave them as is; the AS11 was made by taking into account the SB levels at the AS port and should not become REFL11. We should instead convert one of the old 25 or 33 MHz diodes into a POY55.

We have no plan to change the AS11 PD. I was referring to the AS11 Demod board which currently has the "Demodulator Preamp" circuit installed as a piggy back. In future I will append "_Demod" when I am referring to a demod board, to avoid confusion.

The Demod board with S. No. 022 (being used earlier as REFL11) has been modified.  It now has SCLF-65 as its input LP filter on the PD input line and a PQW-2-90 power splitter.  The unit functioning okay (I and Q signals are 90 deg apart.

The loss of Q output was traced to a possible loose solder joint and we now have both the I and Q signals after resoldering all components in the vicinity of U7 (Ref Schematic of D990511)

There is a strong oscillation around 350Hz present on I and Q signals of both REFL55_Demod and POY55_Demod.  Don't know the source. 

We have run out of power splitters to continue with the Demod board modification. We do not currently have an AS11_Demod board.  All the others are in place and ready for the I<->Q phase angle measurement.

In summary we now have the following Demod boards in place:

[ REFL11, POY11, REFL55, AS55, POY55, POY22, POY110]_Demod

I have posted the attached RF status update and 1Y2 rack layout to the svn.

We have Completed the hardware changes to the full set of 8 demod boards.  The last one completed today is AS11.  I have collected the info on all the demod boards available so far in the table below.  As we measure the actual phase and amplitude unbalance we will expand this table to include new info.

[Steve, Koji, Suresh]

   We shifted two Sorensen power supplies from the Auxiliary rack next to 1X2 to 1Y2.  And have installed them there (pic below).  The local ground reference was picked up from the racks ground reference.  A shielded cable with two twisted pairs was used to make a new power cable for the RF rack.  Since we are using three of the four conductors (+18,+28 and ground), one of them is not connected to anything.  This situation can be improved in a future iteration when, for example, we might wish to relocate the Sorensens to a different rack.

   We are still working on changing the power supply to the RF source.  Will complete this early next week

Key points of the power supply installation

• We followed the grounding configuration for KEPCO except for the signal ground connection
• AC power supply has been obtained from the local power strip. This also provides chassis earthing (for safety)
• The chassis is connected to the shieldin of the DC supply cable. The other end should be isolated.

• The low voltage side of Sorensen's DC outputs are connected in order to share the same reference  level.
• The ground level is provided from the cross connect. The cable is connected between the cross connect ground to the sorencen.
  Unlike the KEPCO case, this cable does not have the current return, but just is to define the voltage level of those Sorensens.

• New AC&DC cables have been nicely strain-relieved.

I measured the amplitude and phase imbalances of the demod boards which have been modified.  This is just a basic health check.  We hope to use the script that Kiwamu is developing for a more accurate test.  The script can also use these measurements as a sanity check.  POP110  requires some further attention. 

The RF distribution box outputs corresponding to the demod board (eg. AS55_LO --> AS55_demod) were used as LO sources.  The RF signal was generated with a Marconi and held a kHz away from the LO frequency.  The amplitude and phase unbalance were measured with SR785.  The RF Power meter was used to check the LO power in each case.

The ~350 Hz noted in the elog below was traced to an RF modulation of the 11 MHz sideband.  This modulation was set up in the Marconi which is currently supplying the 11 MHz local oscillator signal to the RF source.  lt was used during the MC length study completed last week by Valera and Ryan.  The frequency measured was 322 Hz.

As we do not require this any longer, I have switched off this modulation.

[Koji, Steve]

DC power supplies for the RF generation box are now in place. They are the top two of the 6 Sorensens in the OMC short rack next to 1X2.

We made the connections as we did for the RF distribution box, the power supplies labele, and the cables strain-relieved.

The power supply is not yet connected to the actual RF generation box. This should be done by Suresh or someone with the supervision of him.

Note:
We have two +18V supply on the short OMC rack, in total. One is for the RF source, the other is for the OMC PZTs, whitening, etc.
This is to avoid unnecessary ground loop although the grounding situation of the OMC side is not known to me.

[Larisa, Suresh]

All the cables needed for the AS11 PD are in place... the heliax cable runs from the AS table to the PSL rack.  The LO and RF cables to demod board as well as the I and Q cables into the LSC Whitening board are connected.

The cables get rather densely packed when the LSC Whitening filter sits between the PD Interface Board and the LSC AA filter board.  This makes it difficult to access the SMA connectors on the LSC whitening filter.  So we shifted the LSC Whitening and AA Filter boards one slot to the right.  The LSC rack looks like this just now.  We have also shifted the binary cables at the back of the Eurocart by one slot so the same cables are associated with the cards.

I have checked the voltages on the connector.  They are okay and I have plugged in the Sorensen power into the RF Source.  The ground reference for the Sorensens comes from the 1X2 Rack ground reference lines on the south side of the rack. 

I looked for the OMC ground reference. Could not find one on either of the the OMC half racks.

[Kiwamu, Suresh]

In trying to keep the wiring of the LSC rack as neat as possible, we came up with the following channel assignments of the RF PD signals. 

PDI = PD Interface, The PD Interface D-type connectors (#1 to #12) are numbered:  Top -> Bottom and Left -> Right in ascending order. 

The Analog channels on the LSC Whitening Filter boards are numbered similarly, 1 to 32 in four sets.