Currently very busy with target installation in the Hall and the DAQ h/w and s/w.
Nov 17, 2005, Thursday:
Laser#2 (S/N 5324) has been evaluated with the following troubles: PC/Analog board faulty; burnt internal fiber; faulty FAP-I (laser diode); front display to be replaced. Total cost $11,500.
Laser#1 tested. 31.5W through fiber#10 (which is not our best fiber). Shall test the other DuoFAP soon. (We have the other adapter cable now for the interlock.)
Transversity Computer has arrived, and so have the EPR 2" oven windows. The 2" EPR optical elements are scheduled to arrive tomorrow.
The optics box has been setup in EEL Rm 122 by Vladimir. Everything's looks fine. The microswitches for the box interlock system also have been finalized.
Kalyan (from Kentucky) is here to setup the density measurement apparatus. We still need to get a lot more done viz. RTDs, PC w/ RTD boards, DAQ s/w, GPIB/BNC cables, ...
Had a meeting with Chris Curtis of the alignment group, alongwith Bogdan, Alan and Dmitri, to discuss the compass direction measurement procedure. To send Chris the sketch of the layout [PDF] [EPS].
Need to order more optics elements for the compass. Also rails, mounts etc. and send the information to Susan Esp. Finalized (sort of) the final design aspects of the compass mount inside the magnet box (Bogdan, Alan, Susan). Dmitri is making the drawings to modify the compass to include the optical encoder.
Laser # 4 has been sent to Coherent for repairs. The old diode that had 6790 hours on it also has been sent along with it.
Laser # 1 is back after repairs, though it keeps saying External Interlock Open! Mike Benson of Coherent says that sometimes during shipping, the cover interlock screw becomes loose. To check that today (in the day!). Also, the first Duo-FAP system is back after modifications. Yet to test it.
Rocky Mountain Instr. Co. coding expert, Dr. Lu says that the glue used in the BSPC should be able to withstand heat generated by 120-150W laser power without problem. He says the limits are -15°C to +60°C. Although the UVa cube got fried at 150W. Shall talk to Dr. Lu about adhesive capable of withstanding high powers/temperature.
Magnets, soft iron rods, μ-metal rods are all here. A lot of experimentation and testing is going on with the compass. Dmitri Nikolenko is looking at the mechanical aspects of the compass and thinking of new designs and ideas. I am still looking into the optical part of it.
Auto-collimator idea has been successful so far. The latest idea consists of using an optical encoder to measure the changes in the field direction and for quick readout. So, both collimated light beam+auto-collimator and optical encoder ideas will be used.
November 1 milestone has been met. We got a 40% polarization with Carlos with ~50W of laser power. Value using EPR.
Target is in perfect working condition. Only to optimize now. I could do EPR but it's not yet reproducible. Second or third attempt after a first successful attempt fails.
Optical fibers for EPR and Spect. Anal. are here, and so is the EPR function generator. I'm trying the EPR fiber for the first time right now (0021 hrs).
6" mirrors have arrived and so have the mounts (just yesterday!). One of the three mirrors ordered did not pass the tests/inspection, and so will bw delivered by 23rd December.
I'll order the final optics stuff for the compass today in the day.
Mark to make another adapter cable for the other Duo-FAP laser.
Combiner does not heat up at the tip now even with 4 laser at full blast. I'm shooting 2 fans on there, one from each side. Temperature seems to fluctuate between 24 and 25°C.
Oct 12, 2005, Wednesday:
Laser # 4 has trouble. After the 'surgery', the maximum power output at 40A was about 400mW. Coherent FAPsyst expert suspects one of either the power supply, the PC board or the analog circuit has gone bad. We're sending the laser back for repair.
Called Rocky Mountain Instrument company about the temperature dependence of the polarising properties of the BSPC (Beam Splitter Polarizing Cube). Rae said the coding expert will call me sometime today morning. I don't know if he did since I was in a meeting all morning. There is no message on my voicemail.
Electronic requisitions put in for permanent Alnico magnets for the magnetic compass. Also a PO for the laser evaluation.
Yi got the diffuser today (for detection tests for the magnetic compass). He's also looking into Bogdan's idea of damping using a thin brush and air flowing to/from a balloon/bag. Thanks Yi for helping out.
Compass successfully used to get angle changes in the magnet box when the current is changed. Calculations showed that as the current rises from 5.00A to 6.45A, the direction changes by 0.191°.
My future tasks for the compass are 1> Auto-collimator setup (borrow Sirish's for now), 2> Build a gas panel for regulating the air flow to compass and 3> Make an iron magnet structure to create a uniform magnetic field aroung the compass for tests/commissioning.
In today's GEn meeting, the laser/optics work/access bench design was discussed. Also discussed were the magnetic compass platform/support structure inside and outside the target area (magnet box), and the box that contains the connections from the 75m fibers to the legs of the pentopus (the 5-to-1 combiner!).
Alan and Susan said the EPR mount is the same as that from previous experiments, so I can use that straight. Ask Vince.
Combiner tip heating problem seems to be solved. A small fan throwing air at the fiber coupler seems to do the trick. With three lasers now and ~76W, the temperature rises, from 22°C, to 23.6°C. But this temp. is measured at about 4.5cm from the tip, so I have now to investigate how much the temperature really is at the tip.
The adapter cable for the new laser external interlock and it's circuit diagram are ready. I'll pick it up from Mark on Monday.
Sep 28, 2005, Wednesday:
Laser # 4 seems to be functioning alright after a minor surgery!
Analysis of cube power density measurements reveals that it is safe to use the cube under our conditions. Next, trying to talk to the company regarding how the temperature rise in the cube affects its polarizing properties.
All electronic requisitions signed, so things should arrive soon - except the EPR FG, which will take 4 weeks from now.
The compass mirrors are here. Shall try them on tomorrow.
Compass successfully assembled and tested for the first time yesterday. Works well. Has a little 'wobble' from time to time. Shall investigate. Looking into a new damping idea.
Combiner heats up at the tip with lasers at full blast. With two lasers in the new setup, temperature increased by 10C°.
Readiness review meeting was today.
Meeting between Alan and Mark happened last Thursday. Interlock plans and designs were discussed. Alan will design the 'boxes' and Mark will interlock them. The order of interlocks also was discussed. This should now be the safest system ever!!!!!
Sep 20, 2005, Tuesday:
SuperCOLD!! Today again laser #4 shut off with the fault "External Interlock Open!". See here for troubleshooting. I'll do it tomorrow, since we have thunderstorms right now.
Finished off power density measurements at the cube position in the new optics setup. This was done to determine if we are sitting below the damage threshold for the cube, which is 100 W/cm2.
Compass ready to go! Waiting for the mirrors. Have ordered them today.
Laser Safety Interlock System in the Hall: Mark has the first (hopefully final) iteration of the design ready. He's discussed the safety details with Patty Hunt. I'll try to set up a meeting between him and Al Gavalya for the design for interlocking the magnet box to the lasers.
Ordered compass mirrors, EPR and Spectrum Analyzer fibers and optics rails/carriers and the beam dump.
10m fibers ordered, since we will be able to place the EPR diode and the Spect. Analyzer together with the NMR preAmplifier, close to the target area with shielding. Haven't yet heard from anyone on this issue.
The DOE laser safety inspection went well. I hear JLab got an A+! Yeay!!
Apparently, we have a new student on the GEn experiment. No details yet.
Jaideep's GBP vi in LabView v7.0 is working quite well.
Sep 12, 2005, Monday:
Compass ready; need to fix a minor glitch - tomorrow.
Working on new optics setup, and tests.
Jaideep's GBP vi are now in LabView 7.0 version.
Alignment laser is back with new label. Still waiting for the key of the other laser.
Soon to order 10m long 50µ fiber to replace the broken one for the Spectrum Analyzer from OceanOptics. They sent us a catalogue today. We shall place the EPR diode and the spectrun analyzer USB2000 near the target region instead of behind the green wall. So we no longer need the 20m fibers.
Talked to Mark Taylor about interlocking the optics box in the Hall. Final decision will be taken hopefully this Wednesday at our usual meeting. There was no meeting.
Aug 31, 2005, Wednesday:
Magnetic Compass design finalized. Shall give it to the machine shop tomorrow.
Here's the assembly drawing in [JPG] [EPS]. It's not labelled yet.
Combiner optics setup complete in EEL lab. As soon as the cell is put in at 0°, I'll start spin-up comparison measurements and other studies.
Otherwise, trying to master Vladimir's optics simulation.
Patty Hunt took away the other He-Ne laser, which isn't ours. I found it in the cabinet without a key. Since it's Class IIIA, Patty will test it (check it's output power) and send it back with recommendations for use.
Aug 24, 2005, Wednesday:
NMR double peak investigation We rotated the cell by 90° and pumped using 2 lasers (still in 0° configuration). Then rotated the field to 90° (with lasers off) and tried to do a field sweep NMR. Couldn't do it - needed to modify code; so did RF sweep instead. Still see a double peak. So now we have double peak with small coils as well as the large coils of the Helmholtz config. Here's a plot.
Attempting to measure the uniformity of the B-field using a Hall probe. The coils were somehow found to have been turned off. So, we are waiting for the field to stabilize before we do the measurements. Huan Yao has been working with me on points 1 and 2.
On Monday 22nd, Bogdan informed me that a decision has been taken at the meeting that I should work fulltime with Bogdan on the magnetic compass. To that effect,
We've been studying the compass in the new room 125 of the EEL building.
Air flow has been set up, and a box to shield the compass from other air disturbances is in place.
Some ideas for field angle measurement need more thought.
Ways to increase damping are being thought of. I have 3 ideas now which I'll talk to BW about tomorrow.
I've sent out the requisition for two 2.5" long, 0.250" diameter 3N purity iron rods for the compass.
Double sided mirrors are available only for cosmetics and health applications, and no one is ready to make them for us in such small numbers (so far; am still waiting for a few companies to respond).
Did some calculations pertaining to the parallellism of the two FP mirrors. BW is considering replacing it with one two-sided mirror in the center - an idea that has been visited before.
Am setting up the 3rd optics line in the old setup for comparison studies with the new setup. All optics have arrived.
Gaussian Beam Parameters study completed with 6 combinations of 2 lasers, 2 75m finers and 2 legs of the combiner. Am preparing the document now, and working towards the next step.
Aug 14, 2005, Sunday:
EPR was performed successfully on the Rb cell that was polarized in the new lab with one laser (both lines). Here's the first EPR plot and the one after some fine-tuning. The second one is with virtually no background structure - just noise - which is great considering it's such a small signal (~3kV). We currently have electronics from Kentucky (Wolfgang) and might buy the fancy RF generator - the HP E4400B - for ourselves.
Moved to Rm 122 in the EEL building for compass tests. Need to setup air flow controller and two magnets as sources of the magnetic field.
Designs for the compass mounts and laser mounts under discussion with Wolfgang, Al Gavalya, Bogdan and the survey/alignment group. Current idea is to measure the field direction at 5 points along the target chamber. The field will not be tuned to a particular direction, instead we'd simply measure the existing field direction and consider it's components in the required direction during analysis. We'll need a shorter rod for better accuracy, though a thin rod is not desirable since it'll be too soft and easily bendable. The soft iron rod (SIR) we currently use is the 3N5.
Thorlabs optics to arrive Monday morning (Aug 15). Then I'll start the Gaussian beam parameters (GBP) determination process, and measuring the final beam intensity profile at the pumping chamber and at the polarizing cube locations. The GBP need to be determined for various combinations of lasers, 75m fibers and the legs of the 5-1 combiner. We need to know the intensity of the beam at the cube so as to not damage it by going above the threshold of 100W/cm2.
All interlocks in place now and working fine.
Aug 8, 2005, Monday:
Aligned the compass and did a few preliminary measurements. The compass was very stable apart from the fact that the air flow from the oven disturbed the compass quite a bit. Hopefully that won't be a concern in the final reckoning.
All EPR electronics and equipment installed in the new lab. Wolfgang got his fancy function generator, PI feedback box and amplifier from Kentucky. Today, the EPR diode and drive coil have been installed in the new oven, and we are ready to see a signal.
The second laser beam in the existing line has been setup. Need to clean the optics because somehow a lot of dust/dirt has settled on them. If possible, I'll go in tonight and try to clean up the optics.
New compass testing location in the EEL building. Some modifications suggested by Bogdan. I've to give Al Gavalya the drawings for the compass, and work with him on the nesessary design aspects. Note: SIR=Soft Iron Rod
Aug 2, 2005, Tuesday:
Aligned the Fabry-Perot etalon with the alignment (He-Ne) laser. Shall test the temperature dependence now.
Discuss about the mounts for the laser(s) in today's meeting. The idea is to secure the alignment laser onto a V-mount in the Hall (with shielding) so that there is no position/angle reproducibility error. This is to set the field at a specific angle. If the field needs to be oriented at more than one angle, we need more mounts and preferably more lasers.
Shall plug the compass in at the next available moment and do field direction measurements. For now, using the same legs as the original design.
Aug 1, 2005, Monday:
Everything set in the new lab, and we have the first helium NMR signal today. The Aug 1 milestone has been met!
The laser interlock relays have not yet arrived.
Installed the compass in the magnet box. Wasn't smooth. Legs were damaged. Need to modify design.
The new oven window might be reflecting a little too much light! Will have to check that.
July 26, 2005, Tuesday:
Placed order for mirrors via GEn account (earlier had it on Hall A account). Waiting for response regarding breadboard to order other optics stuff.
Chiranjib and Kalyan looking into making RTDs for the temp. interlock.
Final optics alignment done with Coherent laser (very low power). Now the laser can be turned on anytime to start pumping.
Soldered the electrical components of the new laser interlock box. Mark has ordered the relays, and as soon as they are here (1, 2 days), the I.B. should be ready, and lasers can be turned on simultaneously in both labs.
Wolfgang coming on Aug. 2
July 25, 2005, Monday:
Set the optics line to a lower level. There were some problems with the unistrut mirror mount system with respect to alignment. Fixed everything. Now the beam can go to the cell with two mirrors.
Doing analysis - henceforth, this point shall not be noted in this section.
Measured the current distance from the center of the pumping chamber (PC) to the polarizing cube - ~5.2m
Compass ready to be installed
In the process of making RTDs for the fiber temperature interlock system. sHALL TALK TO mARK AND cHRIS TOMORROW
Got the alignment laser back from Patty Hunt. Milles Griot to send us another label saying the laser is class IIIA and not IIIB as the earlier label said (and the reason why Patty took away the laser in the first place).
Gave out order for the 6" mirrors and their mounts. Ordered 2 spare mirrors (since they have a shipment time of 6 weeks) and 1 spare mirror mount (4 weeks lead time). (Newport) Earlier, 4 such mirrors were required and, given the price of each mirror, that was too expensive. So the design was modified, and now requires only 2 mirrors in circuit (so we can have 2 spares too).
Also ordering other optics stuff like lenses, mounts, breadboard, etc. (Thorlabs)
July 19, 2005, Tuesday:
Compass leg back from machine shop
Doing analysis
Moved things around in the lab.
Finalized optics material to be ordered with Vladimir. Shall discuss it in the Wednesday GEn meeting. The 6" mirrors have a lead time of 6-7 weeks at Newport. Shall call Thorlabs tomorrow. The price of each mirror is around $1800.
The optics line to be set to a lower level now, since a compensating mirror is added to the "circuit" (which should have been the case to begin with). Made a big new hole in the plastic screen!
July 18, 2005, Monday:
Compass leg has troubles - given it back to Casey from the machine shop, to fix.
Doing analysis
Need to talk to Vladimir about latest design and ordering of material.
July 15, 2005, Friday:
Alignment of optics line complete. Light now goes in from the wall side of the box into the box. All optics are set at pumping cell level, so there's only one mirror taking light to the cell i.e. uncompensated. So, the circular polarization of the light is reversed. This configuration can be easily changed to incorporate two mirrors, but currently we do not have any more 4" mirrors.
Interlocks working; circuit included in the LSOP. Everyone to sign the LSOP ASAP. All those whose name does not appear there should contact JP.
Coherent manual brought to the new lab
Compass legs arrived - 4" long with 2" of thread (3/8-40).
July 14, 2005, Thursday:
Alignment of optics line complete with red He-Ne alignment laser
All necessary optics instruments in the lab
Compass legs design given to machine shop yesterday
The new laser interlock box will be ready soon. Currently the box in the EEL lab is in place in the new lab. Mark Taylor has given the parts for the new box to be made, and Chris Cuevas is going to teach me to integrate the whole thing (since Mark is going on a vacation next week). (Hope I have good soldering skills!)
Ameya Kolarkar
Last modified: Sat Jan 14 20:18:37 EST 2006
