The Alpha Magnetic Spectrometer

1
(No Transcript)
2

• Development of Thermo-Mechanical Pump and Liquid
  Acquisition Device
• Dr. Nick Shaw
• Scientific Magnetics

3
SUMMARY

• Background to liquid helium management in
  low-gravity
• Development of the LAD (liquid acquisition
  device)
• Development of the TMP (thermo-mechanical pump)
• Testing sub-assembly of LAD/TMP/Current leads

4
Background

• Helium vessel must vent to space vacuum through
  porous plug
• Helium has to be pumped using TMP to cool the
  current leads and to re-cool the magnet
• Location of helium unknown at zero field due to
  low gravity environment
• Helium is diamagnetic and will therefore be
  repelled from regions of high magnetic field

5
Diamagnetic effect on He
Wick 30cm against force of 1 milli-g
Equivalent to wicking 0.3mm in earths gravity
Circumferentially, the force is two orders of
magnitude smaller
6
Design of LAD

• Constructed from 9 micron E-glass fibres
• Approx 6 micron hydraulic diameter capillaries
• 25 mm outer diameter
• 19 mm diameter knitted core
• 3 mm radial thickness outer braid

7
TMP Apparatus
8
LAD test apparatus
9
Testing the LAD (length)
10
Testing the LAD (height)
11
Development of TMP

• ILK design used a ceramic element
• We were concerned about its stability and
  longevity
• Extensive testing and re-design

12
Sintered Stainless Steel element

• We obtained a sintered stainless steel element
  made from 0.2 micron particles
• The element was 25mm diameter and 9mm thick
• Results were very encouraging

13
Evaporator Heater

• The ILK design had an evaporator chamber with a
  second heater
• Unable to obtain higher flow rates and pressures
  when using the evaporator heater
• Tested removing the evaporator chamber completely

14
Removing the Evaporator Heater

• Very similar results between TMPs with and
  without an evaporator chamber

15
Double Thickness Element

• A final test was performed with a double
  thickness sintered stainless steel element
• Doubling thickness reduces the normal component
  reflux
• Improved pressure and flow rate were seen at all
  powers

16

• The design of the current leads is complicated
• Engineering model is a straightened version of
  the flight leads

17
Current Leads Instrumentation
The LAD/TMP combination was used to cool the
engineering model
18
Operating Current Leads with TMP
19
Flight TMP Manufacture

• Flight TMP components received from ILK
• Drawing modifications are underway

20
Conclusions

• The LAD exceeds minimum specification by two
  orders of magnitude. Testing has been completed
  successfully.
• The TMP has been redesigned to eliminate the
  ceramic elements
• Further improvements have resulted in a simpler
  design without an evaporator chamber
• Operation of the LAD and TMP combination with the
  engineering model of the current leads has shown
  that the current leads are stable at maximum
  current with helium flow rates of 100 mg/s at 100
  mbar

21
CURRENT LEAD LAYOUT
Pneumatically operated mechanical disconnects

• Small metallic cross- section
• Complex configuration
• He vapour cooled

TMP produces gt100mg/s helium gas flow rate
22

• When charged, the coils develop mutual magnetic
  loads which are reacted internally. The magnetic
  loads are considerably larger than inertial
  forces.

23

• The coils are cooled to a temperature of 1.8 K by
  a system of pipes

24

• connected to a 2500 litre superfluid helium
  tank.
• The cold mass is suspended from a system of 16
  composite straps.

25

• The coils and helium vessel are enclosed in
  radiation shields and multi-layer superinsulation.

26

• All components are suspended within a vacuum tank.