Polhe3 target lab howto
Contents
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.
oven (micromega) 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).
Impedance matching
field setup
use the 3D_rotation labview program to setup, but it won't give you real feedback.
try to read the number off the power supply.
for large coil providing longitudinal field of 25G, it has 22.5V and 7.21A
