NAOJ GW Elog Logbook 3.2
With help from Takahashi-san, I closed the vacuum chamber.
I didn't start pumping since I would like to monitor the operation of the pumps over a few hours from a safety point of view (since they haven't been operated in quite a while). Also, I haven't set up any DAQ system to log the pressure. I will start pumping this Thursday or next Monday.
Overview: I modified the vacuum connections around the TMP.
Before: The TMP is located at the bottom of the cryostat with a gate valve and 6-way cross fitting in between. The cross fitting has CF (-250?) flanges on either side with four "KF ports" on the cylindrical body. The "KF ports" are located after the gate valve. The outlet port of TMP is KF16 and connected to a "KF16-KF25 adaptor". This adaptor is connected to a "Right angle valve", which is connected to a "KF25 TEE" fitting. One end of the "TEE" fitting should be connected to the scroll pump with a flexible vacuum hose. The other end of the "TEE" was attached to one of the "KF ports" with another "Right angle valve". The remaining "KF ports" had a vacuum gauge, a Swagelock poppet check valve and an inlet valve.
Changes: I replaced the swagelock poppet check valve with a blank flange. Furthermore, the "Right angle valve" on one of the "KF ports" connected to the "TEE" with a flexible vacuum hose was removed and replaced with a blank flange. The "Right angle valve" was connected to the "TEE" with a "KF25-Swagelock adaptor" connected to the other end. This adaptor will be used to inject Helium during warm-up.
Items: For this work, I brought the following items from TAMA: 2*KF25 Blank flanges, 3*KF25 hinge clamps, 5*KF25 O-Rings and 1*KF25 full nipple fittings. Additionally, the "KF25-Swagelock adaptor" was brought from KEK.
NOTE: I noticed the KF16 outlet port was not tightened. I tried to tighten it, but it was still loose. Not sure if this is normal.
I installed a temperature sensor (brought from KEK) on the breadboard inside the cryostat (photo). It is connected to wire bundle C2. I think there is a temperature sensor mounted on the cold-head but I can't find which pin feedthrough it is connected to (this wire perhapas).
z = 74.5,mm, Pt = 4.81W : Sat, Apr 6, 2024 10-14-17 AM.txt
z = 44.5, Pt = 4.87W : Fri, Apr 5, 2024 9-52-57 PM.txt
z = 54.5mm, Pt = 4.87W ; Fri, Apr 5, 2024 5-12-55 PM.txt
z edges seem to be at 39 and 90 mm. z_center = 64.5mm
The DC is still slowly decreasing with increasing z from aboiut 5 to 3 V... depending on measurements results I might aligned DC to specific z.
map at z_center : Fri, Apr 5, 2024 1-13-49 PM.txt
Installed the 30mm diameter , 120mm thickness sample (1623048-4) called 120#1
I moved z_IU to 18.51mm
pink tape is at bottom towards IU
the sample is held roughly t its central thickness position to limit its tilt that could misaligned the beam on the sensors.
in that configuration, the DC is still varying between about 2 to 5V while changing z from 20 to 120mm...
Pt = 27.0mW ; Pin = 31.3mW
Pt = 4.72W
long z scan at x,y centers : Fri, Apr 5, 2024 11-52-43 AM.txt
During Yuhang's Christmas visit we attempted to replace the TAMA OPO. It was aligned but could not take a scan signal - the high voltage driver would just zero out then turn off, suggesting that the PZT on the input mirror is broken. I have to disassemble the "new" OPO and replace the PZT. The connectors for the PZT are soldered to our Dsub box - the OPO was kept in a zip lock bag during soldering. The Dsub box connects the OPO PZT and temperature actuator wires and puts them on a Dsub port, which then plugs into the controls of TAMA electronics.
I measured the output power vs current of the Coherent Mephisto laser in the ATC cleanroom used for the Taiwan and Korea experiments, using both standard Thorlabs (up to 500 mW) and thermal (several W) power meters. I fixed the laser temperature at 24.21 C. The output of the laser is about 47 mW at 0.8 A, up to 1.17 W at 1.5 A (it can go higher but I stopped here).
In the leadup to the Taiwan/Korean Christmas visit I designed the input beam path to: 1) inject collimated infrared p-polarized light into the Taiwan fiber SHG (~2.3mm diameter), and 2) send a small amount of s-polarized light to the Korea Faraday isolator. The actual beam profile was measured by Yi Ru Chen. There is a HWP and PBS setup which transmits p-pol to Taiwan (SHG) and reflects s-pol to Korea (Faraday). I set up to reflect a small amount of s-pol to Korea. At 0.800 A laser current, 30 mW reaches the HWP, with 3.8 mW s-pol going to Korea and 25.1 mW p-pol going to Taiwan. 3.8 mW is reasonable for our OPO characterization, it's about what we used last time. There is plenty of room to adjust up or down anyway, and since the beam size going to the OPO is around 20 micron the intensity is quite dangerous even at 4 mW.
I constructed a beam path to travel across the indicated line on the breadboard, cutting off from the Korean FI path (they aren't going to come back until October). The beam travels horizontally at 75mm, the height of the OPO crystal. In a previous iteration of this test we had a rotation stage below the OPO for rotation alignment but we found it to be unnecessary. It is better to set a beam at constant height, rough align the OPO case by hand then fine align with steering mirrors. We also did it this way in TAMA twice during the replacement/re-replacement episode and it works fine, could achieve > 90 % mode matching quickly. The beam path should be collimated at 2.3mm for quite some distance, so based on this I can set up a system to send the beam through an EOM. The lenses we originally used to mode match to the OPO (40 and 75 mm) are in the ATC unused.
I took a soldering iron from the elec shop and the Beam Master beam profiler from birefringence compensation. For other instruments the ATC KOACH cleanroom now has the 8 GHz function generator, PZT high voltage driver, Thorlabs temperature controller, resonant EOM, oscilloscope, old TAMA spectrum analyzer, PDA05CF2 RFPD, DET10N/M biased PD. We can scan the PZT of the reassembled OPO to test mode matching but to lock I would need another function generator or mokulab. The CCD and TV screen were taken to speed meter but maybe I don't need them. Locking is probably unnecessary though. It seems based on previous calculations that, due to the short length and low finesse, the storage time is too short to determine internal loss from cavity ring-down, even with a nanosecond scale off-switch. We will need to wait until the sqz/antisqz measurement to really see the optical loss.
z = 73.75mm, Pt = 4.87W : Thu, Apr 4, 2024 10-28-30 PM.txt
z = 53.75mm, Pt = 4.85W : Thu, Apr 4, 2024 6-30-57 PM.txt
edges at 48.5 and 79 mm : z_center = 63.75 mm
map at z_center : Thu, Apr 4, 2024 2-23-48 PM.txt
I installed the 30mm diameter; 70mm length, 4/6 sapphire (T70#3) with pink tape at bottom towards IU.
Realigned DC
Pt = 26.3mW ; Pin = 30.7 mW
Pt = 4.87W ; long z scan (as for all previous z scan at x,y center ie 327,119 mm) : Thu, Apr 4, 2024 11-59-20 AM.txt
edges at 48.5 and 79 mm : z_center = 63.75 mm
map at z_center : Thu, Apr 4, 2024 2-23-48 PM.txt
z = 53.75mm, Pt = 4.85W : Thu, Apr 4, 2024 6-30-57 PM.txt
z = 73.75mm, Pt = 4.87W : Thu, Apr 4, 2024 10-28-30 PM.txt
z = 66.5mm, Pt = 4.83W : Wed, Apr 3, 2024 9-59-53 PM.txt
I swapped the R and L cables for the OPO mixer.
During this process a cable for CC PLL monitor was quite damagedd but it's a bit tedious to replace alone and not priority for now so I left it as is for now.
I finalized the new box connections and little cable tidy up.
I could lock SHG after changing the DDS1 DAC1 phase from 20 to 240deg and the servo gain from 0.9 to 0.1 to avoid ringing. I measured about 30% HOM still present and 235mW of green produced.
The MZ/GRMC are heavily misaligned and I'll recover them tomorrow.
I've installed my two supports, made using a 3D printer, for the LCD (from the screen of a monitor).
The beam of the setup is too low to path throw the LCD screen. So I added to more mirrors (2 inches) to get the beam higher, and I started to align them.
z = 46.5m, Pt = 4.73W : Wed, Apr 3, 2024 5-28-27 PM.txt
Installed T70#2 (30; 70 mm 5/6)
pink tape at bottom towardsiu
realigned DC
Pt = 27.4mW ; Pin = 31.5mW
long z scan Pt = 4.77W ; Wed, Apr 3, 2024 12-31-34 PM.txt
z edges at 36 and 77 mm : z_center = 56.5 mm
map at z_center : Wed, Apr 3, 2024 1-11-48 PM.txt
z = 46.5m, Pt = 4.73W : Wed, Apr 3, 2024 5-28-27 PM.txt
z = 66.5mm, Pt = 4.83W : Wed, Apr 3, 2024 9-59-53 PM.txt
I finalized the mixers box and installed it in the bottom NIM rack.
A little issue is that the BNC mixers are a bit too large to close the box... However we still have quite some space in the NIM racks so I'll leave the box open for now.
I'm also taking this opportunity to change cables for more appropriate ones and passing them through the cable clamp.
One thing I'm not sure about is that OPO RF signal was sent to the 'L' port of one mixer which I thought was for LO..
I'll correct this.
I swapped the R and L cables for the OPO mixer.
During this process a cable for CC PLL monitor was quite damagedd but it's a bit tedious to replace alone and not priority for now so I left it as is for now.
I finalized the new box connections and little cable tidy up.
I could lock SHG after changing the DDS1 DAC1 phase from 20 to 240deg and the servo gain from 0.9 to 0.1 to avoid ringing. I measured about 30% HOM still present and 235mW of green produced.
The MZ/GRMC are heavily misaligned and I'll recover them tomorrow.
Today I switched aircon of central building to cooling mode at 22degC.
Still need to be done for END.
z edges seem to be at 39 and 90 mm. z_center = 64.5mm
The DC is still slowly decreasing with increasing z from aboiut 5 to 3 V... depending on measurements results I might aligned DC to specific z.
map at z_center : Fri, Apr 5, 2024 1-13-49 PM.txt
z = 54.5mm, Pt = 4.87W ; Fri, Apr 5, 2024 5-12-55 PM.txt
z = 44.5, Pt = 4.87W : Fri, Apr 5, 2024 9-52-57 PM.txt
z = 74.5,mm, Pt = 4.81W : Sat, Apr 6, 2024 10-14-17 AM.txt