Progress Report

1

• Progress Report
• 900 MHz NMR Probe Cryogenic Gas Supply System
• Team 2
• Rebecca Altman
• Jason Kitchen
• Zachary Stevenson
• Jessica Vanterpool
• January 29th, 2009

2
Presentation Outline

• Project overview
• Changes in project scope
• Baseline testing of system performed last week
• Assembly and fabrication progress
• Purchase summary
• Upcoming tests of system

Team with Dr. Brey in front of 900 MHz magnet
3
Project Overview

• Improve efficiency of existing cold gas delivery
  system to cool NMR samples to 103 K, with 0.2 K
  temperature regulation
• Design an automatic refill controller so liquid
  nitrogen heat exchanger cryostat will remain full
  during long duration NMR experiments

Cold gas delivery system schematic
4
System Hardware
5
Project Scope Update

• Contacted Cryofab Inc. with the details of our
  design for the NMR probe dewar
• Lead time on the manufacture of the new dewar is
  8 weeks
• Not enough time to assemble and test as a part of
  this project
• Based on sample temperature measurements of 106 K
  achieved last week, redesign of probe dewar no
  longer a priority
• Sponsors and team both agree to shift this focus
  to maintaining sample temperature stability
  during cryogen refill

Rigid stainless steel probe dewar
6
January 21, 2009 NMR Test on 900 MHz magnet

• Purpose of test was to compare probes T-type
  thermocouple measurement to sample temperature
  and calculate ?T
• Test used lead nitrate spinning at 5.0 0.1 kHz
  to detect 207Pb spectrum
• NMR signal peak shift is temperature dependent,
  approximately 0.753 ppm / C

Bielecki, 1995
7
January 21, 2009 Experimental Results

• Lowest achievable sample temperature was 105.9
  0.1 K
• Unexpected results showed average ?T of -8.8
  2.7 C from thermocouple to sample, could be from
  N2 gas rapid expansion in stator

8
January 23, 2009 NMR Test on 900 MHz magnet

• Purpose of test was to confirm probe could
  achieve a stable temperature target by detecting
  NMR spectra of a sample with a well-known phase
  transition at a particular temperature
• Test used single crystal ammonium dihydrogen
  phosphate (ADP) spinning at 5 kHz to detect 31P
• ADP undergoes a solid phase transition at its
  Curie point, becoming antiferroeletric at
  approximately 148 K

Sen, 2007
Sen, 2007
Sen, 2007
9
January 23, 2009 Experimental Results

• NMR spectrum showed the phase transition at a
  probe thermocouple temperature of approximately
  156 K
• 156 K average ?T 147.2 K confirming lead
  nitrate test ?T

Temperature regulation interface
10
Assembly Progress

• HX (Heat Exchanger) fabrication
• Design modification
• Single set of coils easier to fabricate than
  concentric dual coils, so 13 coils were made
  instead of 8 inner and 8 outer coils
• Coils were then attached to bottom of the HX
  using brass compression fittings (leak tight in
  LN2)

13 loop HX
11
Assembly Progress

• Refill Controller
• Rear plate and component mounting board machining
  is complete
• Nut rivet inserts installed in component board
• Single switch relay and the barrier terminal
  block were screwed onto the board
• Board screwed onto box

12
Assembly Progress

• Solenoid Valve
• 110 V AC cryogenic rated solenoid valve
• Wires were soldered to electrical connection,
  shell of connector is threaded so valve cannot
  become accidentally unplugged
• Strain-relief grommet was added to valve so wires
  will not break free

13
Purchase Summary

• Total dollars spent to date for refill
  controller 340
• All components have been received for refill
  controller
• Need to price pneumatically-actuated cryogenic
  valves
• Need to price a standard vacuum insulated
  transfer line for connection between supply dewar
  and HX cryostat

14
Planned Testing

• February 2nd Run system to determine rate at
  which LN2 is consumed by the HX
• February 10th Run system venting N2 vapor inside
  cryostat past the HX precooling coils
• Compare to rate of normal LN2 consumption
• Determine what effect precooling has on the
  sample temperature
• February 10th Test new 13 loop HX coils
• Confirm temperature output for given flow rate
• February 17th Run system and vary time between
  refills
• Compare sample temperature stability during a
  long refill period with a short refill period

15
Summary

• Experimental results show system can achieve 106
  K, temperature difference between thermocouple
  and sample verified by ADP test
• Based on experimental temperature results and
  vendor lead-time, redesigned probe dewar removed
  from project scope
• Temperature fluctuations over 2 K during start
  of refills adds a new task to improve system
  performance
• Assembly of refill controller on schedule, should
  be completed by middle of February for later
  testing of automatic refills
• Pneumatic actuated valves need to be researched
  and purchased due to concerns of solenoid valve
  in 900 MHz magnetic field