Difference between revisions of "Polhe3 target lab howto"
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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. | 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 | + | after tuning, the coils around target can reach 3mV and the coil B around pumping and outside oven can reach 30mV. |
| − | The coil | + | The coil A around pumping and inside oven has bad contact with over 2k ohm, but it still have read out. |
== making pickup coil == | == making pickup coil == | ||
Revision as of 21:23, 5 March 2012
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.
air flow setup
At about 500, it's slow enough to reach higher temp by heaters and fast enough to bring hot air down to oven.
Omega RTD control setup
It's used to controlled one heater on/off while another heater is always on.
only output 1 is used which is linked to setpoint 1.
In "out 1" setting, the auto PID should be disabled as it doesn't work well for our system with slow response. use D=0, I=3999 seconds (means integral over long history for slow system) and P=001.0 - 010.0 C (means larger to smaller effect)
To reach highest temperature (currently 230C without RTV sealing around oven bottom), we need large effect of P, ie p=002.0 or 001.0
For F3105 RTD, the type should be set as 385.3 where 385 mean the resistance-temp coefficient is 0.00385ohm/C and 3 means 3-wire connection.
refer to its manual in lab
Newport RTD control 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
we use setting: AC, band pass 10k-100k, low noise, 50ohm output, gain 5 (pumping) 2 (target), input B (pumping) A-B (target)
we are not using pumping pick up coil A inside oven because it has bad contact.
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 B around pumping and outside oven can reach 30mV.
The coil A around pumping and inside oven has bad contact with over 2k ohm, but it still have read out.
making pickup coil
The coil can be approximated by Parallel LC circuit, refer to http://en.wikipedia.org/wiki/RLC_circuit#Other_configurations and http://www.cliftonlaboratories.com/self-resonant_frequency_of_inductors.htm
The pair of coils should be made with same gauge wires and same turns so that their self resonance frequency peaks are close to each other.
Our testing frequency about 91kHZ should be away from the self resonance frequency peak and be verified with Q curve measurement.
The coil inside oven need to have RTV as adhesive instead Epoxy for outside coil.
Wires should high temperature type (the thin one is lab).
