Polhe3 target lab howto
Contents
Optical Alignment
use "cross laser aligner" to do initial alignment of the cube and mirrors, then use laser in low power mode (maybe 5-10na) to do fine tuning by looking at the spots on the mirror close to target. Try to focus on aligning the main light spot, not many of the weaker reflections.
make sure the reflection not going to laser fiber directly, try to guide it on the side to avoid burning the coating on the fiber.
The light should going to the one side of the split cube. The right side has a dot on the corner.
Quarter waver plates calibration
The configuration is laser (light has no pol)-> split cube #1 (linear pol)-> quarter wave plate #1 (circular pol)-> quarter wave plate #2 (linear pol in another direction)-> split cube #2 (light deflected)-> light intensity detector.
quarter wave plate #1 need to be calibrated ahead, then adjust the #2 to have lowest light output so that wave plate #2 is calibrated well.
(copy the record on notebook here)
3/15/2010
COMET LASER (JLAB #1)
half power - 12.2 W
I=30A T=20C
| 1/4-Wave Plate | Angle | Residual Power |
|---|---|---|
| #101 | 286° | Reference |
| #102 | 214° | 272 mW |
| #19 | 127° | 256 mW |
| #16 | 330° | 185 mW |
| #21 | 240° | 165 mW |
| #2 | 76° | 55 mW |
| #25 | 120° | 164 mW |
| #20 | 225° | 114 mW |
Also #17 and #7 are identified as half wave plates.
Theormal RTD setup
CNFG ↓ ALR2 ↓ ENBL-AbSo-ALRL-ALRH
ENBL: enable ALR2
Abso: change the mode to absolute
ALRL: Low temperature limit
ALRH: High temperature limit
buttons:
first button: direct to menu in the same level
second and third: change the settings
fourth: direct to submenu or save the display
more details please look at the page 32 instruction book
NMR Pre-amplifier configuration
refer to page 5 Improving SNR for water calibration of the polarized 3He NMR system
NMR pickup coil tweaking
Minimize the RF signal in NMR pickup coil.
pickup coils are in pair around target chamber and pumping chamber. Each of them should have about 20 ohm.
keep laser off, keep RF signal output to large value like 3.2Vrms and 88kHz, adjust the screws to make coils rack tilt (large effect) and/or coil rack slide (small effect). Watch signal from output of the pre-amplifier in an oscilloscope, make model A, B minimum, then A-B minimum.
after tuning, the coils around target can reach 3mV and the coil A around pumping and outside oven can reach 30mV.
The coil around pumping and inside oven has bad contact with over 2k ohm, but it still have read out.
