Polhe3 target lab howto

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Revision as of 15:04, 27 July 2013 by Zwzhao (Talk | contribs) (oven RTD control setup)

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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


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

photo of the pre-amp

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