PPMS family of instruments. April 2014

Transcription

1 PPMS family of instruments April 2014

2 outline PPMS family wet: PPMS, EverCool, EverCool- II (SQUID also) dry: Dynacool, VersaLab Temperature control all but VL: He gas flow VL: thermal switch Field control persistent switch no pers. switch Chamber control states: vented, flooding, purged, sealed... valves pumps

3 3 kinds of messages we will have educason How does it work? seung the course How do I use it? ensuring arrival What can go wrong? look for these icons throughout talks...

4 family tree branch #1: MPMS and progeny available today: MPMS MPMS-XL (MultiVu) MPMS 3 MPMS 3 EverCool PPMS (branch #2) MPMS options MPMS EverCool low field oven fiber probe RSO EDR high pressure A.C. transport EDC rotator Helium-3

5 family tree branch #2: PPMS and progeny available today: PPMS PPMS DynaCool Reliquefier for PPMS VersaLab PPMS options PPMS EverCool EverCool-2 ACMS ACT Heat Capacity TTO VSM Dil. Fridge high pressure Resistivity Hi Vac Torque Helium-3 VSM oven ETO SPM

6 PPMS family: our focus here VersaLab PPMS PPMS EverCool- II DYNACOOL

7 Unique Cryostat Design Vacuum Space Cooling Annulus Sample InserSon Tool Sample Puck Sealed Sample Chamber 12- pin Connector

8 PPMS Sample Puck 12-pin connector Heat Capacity Microcalorimeter AC Transport Puck

9 PPMS inside Cooling flow Pump ATL or Goodbye! Dewar boiloff ATL or Goodbye! Dewar isolason vacuum Liquid Helium 4.2 K, 1 atm Probe isolason vacuum Cooling annulus Shield SuperconducSng magnet Sample chamber Sample K

10 PPMS EverCool inside Pump G- M Cryocooler Liquid Helium 4.2 K, 1 atm Condenser EverCool- II improves uses more efficient gas cooling gas- only cooldown more efficient QD- made compressor

11 DynaCool inside Pump Shield Bucket pulse tube Cryocooler in gas Efficient use of available cooling Inherently vibrason isolated Large, solid copper links to magnet Large A/L, simple Helium flow cooled by direct contact with cryocooler Large gas flows without affecsng magnet temperature vacuum! 4 K plate

12 VersaLab inside 4 K 40 K vacuum! smaller 0.1 W G- M cooler runs on 1- phase 220 V 1 st stage (40 K) cools radiason shield chamber via thermal switch 2 nd stage (4 K) cools SC magnet cryopump charcoal

13 PPMS probe: closer look

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15 Temp. control: PPMS and Dynacool He gas flow cools chamber heaters in chamber block & neck dual impedance main (ON/OFF): 0 5 gas liters/min. low temp ( CLT ): 0.7 liters/min. range: K (1.9 K for PPMS) PPMS probe

16 Temp. control Sps use sinter filter on transfer line to clean L- He change scroll pump Sp seals EverCool, Dynacool 3-6 months interval, as needed low- T bump on pre PPMS systems wait at 20 K to ensure monotonic cooling app note

17 persistent mode (top) saves LHe very quiet field driven mode (bokom) takes ~20 sec to change modes Magnet control: PPMS

18 magnet control: Dynacool and VersaLab magnet always driven filter removes noise in B- field magnet is solid conducson- cooled magnet temp. monitored magnet power supply filter (~ 100 ohms) SC magnet

19 magnet control Sps reported field based only on current in magnet power supply no field sensor in chamber accuracy issue for B < 1 T app note

20 chamber control Seal: isolate chamber from outside Purge/Seal: 3x flush and pump from dewar boiloff (PPMS) gas bokle (DC, VL) Vent/Seal: leaves at 1 atm Pump Cont.: keep pumping w/ mechanical pump, gets to ~1 torr rotary vane (PPMS) diaphragm (VL) scroll (DC, PPMS EC- II) Vent Cont.: keep flooding w/ gas HiVac: cryopump acsvely pumping

21 chamber control Sps maintain clean oil in rotary vane pump regenerate cryopump charcoal as needed upper neck region can stay cold aoer block warms to 300 K ices up if vented: wait 1 extra hour at 300 K pressure gauge calibrason is coarse, tells: vented purged HiVac

22 wiring on sample chamber twisted pairs of low resistance Cu alloy running in annulus à thermal exchange w/ He gas roundtrip resistance from Lemo connector ~1.1 ohm each wire 1m of length 0.32mm diameter approx. 100 pf capacitance to ground rasngs 50 V DC max 500 ma max consnuous End