General Purpose Decay-Channel Spectrometer (GPD)

General Description

• Beam properties
• Area: µE1
• Positive or negative muons: momentum ranges ~60-125MeV/c.
• Muon range: ~1.5-20g/cm², range width ~30mg/cm²-~4g/cm² FWHM in CH₂.
• Polarization: Longitudinal (direction of the muon momentum; no spin rotation).
• Collimation : Cylindrical collimation with dia. 16, 12, 10, 8, or 6mm. Rectangular collimation 4x10 mm.
• Collimated beam: Beam profile monitor is available for checking quality of beam and tuning collimator positoins in magnetic field (see instructions here ).
• Degrader: Silver or kapton layers are used as muon degraders.
• Detectors (fast plastic scintillators, Hamamatsu-PTs R1828-01, PSI voltage deviders PHVR100,
  iseg HV-powersupply HPp 30 107):
• Incoming muons: 'M' (between collimator and sample; 2mm thick plastic scintillator).
• Decay positrons (electrons): 'forward' (single, fork), 'backward' (single, fork),
  'up' (pair), 'down' (pair), 4mm thick each.
• System time resolution: ~1ns.
• For more information on the detectors click here or see the NIM-electronics logic diagram pTA version).
• Magnetic fields operating instructions:
• Static zero field compensation (dynamic compensation is in preparation).
• Main field 0-0.66T, parallel or perpendicular to the muon spin (rotatable coils).
• Remotely controlled movable parts: The following parts are equiped with stepper motor drives and can be controlled by DELTAT under Modify Devices... smngpd...: GPD_VERTICAL, GPD_HORIZONTAL, DEWAR, DEGRADER, COLLIMATOR and DETECTOR (more channels are available).

Please note: It is extremely dangerous to run the motor drives without checking the free mobility. Because in most cases remote motion is necessary when working with transverse field, instructions and warnings are given in detail under operating instructions for magnetic fields and for the motor drives. Please read it carefully.
• Available temperature range 0.3 - 500 K using different types of cryostats (see below).

Samples

• The users are expected to bring their own sample holders and make sure that the samples are safely sealed and fixed on the holder.
• Users who intend to bring hazardous sample materials (radioactive, toxic, flammable, etc.) to PSI should read the instructions on our safety page well in advance of their scheduled beam time.

Available Sample Cryostats

Oxford Sorption Pumped ³He Cryostat type Heliox/Variox ²⁾

The VARIOX-cryostat is a top loading ⁴He-bath cryostat with variable temperature insert useful in the temperature range 0.3 - 300 K (details). The large sample chamber (50 mm diameter) is filled with ⁴He contact gas and contains the sample suspended on a sample stick. Alternatively, the sample stick can be replaced by a ³He-insert type HELIOX.
The HELIOX-insert is a sorption pumped single-shot ³He-cryostat. Its main components, the sorption pump, the condenser and the ³He-pot are connected to form a closed ³He-system. The ³He-pot is inclosed in a separate vacuum chamber which also contains the sample mounted on the pot. The sorption pump and the condenser are cooled through the ⁴He contact gas by the VARIOX variable temperature insert.

Temperature Range
• 0.3 - 300 K
Holding Time
• >40 hours
Coolant
• 40 litres/day liq-⁴He consumption, automatic refilling
• 10 litres/day liq-N₂ consumption, automatic refilling
Maximum Sample Size
• 40 mm diameter. See a drawing with main dimensions.

The system is relatively easy to operate. Control is due to a highly automated LabView program (details). However, sample change is rather time consuming. It takes 6 - 8 hours to change a sample in the HELIOX including cooling down.
Sample rotation
• 0 - 360^o available on request

For more details refer to the user instructions.

Janis ⁴He Vaporizer Cryostat²⁾

Top loading type with continuous He-flow through sample chamber, mounted on vertical spectrometer axis, sample rotation about vertical axis, pneumatic retraction of the sample from beam axis.
(more details).
Temperature Range / Coolant
• 2.5 - 300 K
• 4 - 0.7 litres/hour LHe at 4 - 25 K
• 0.7 - 0.4litres/hour LHe at 25 - 75 K
• 0.4 - 0.2 litres/hour LHe at 75 - 300 K
Sample rotation
• 0 - 360^o available on request
²⁾ Please Note: the Janis and Oxford cryostats can only be allocated separately in larger beam-time blocks (separated by at least one week) because of long changeover times.

Closed-Cycle Cryostat (CCR)³⁾

Cold finger type CCR, no contact gas. Mounted on horizontal spectrometer axis. Temperature Range / Coolant
• 12 - 300 K
• No coolant (He-gas compressor)
Recommended Sample Holder and Maximum Sample Size: For an overview of all available drawings, click here.

New Chemistry Cryostat³⁾

Top loading type with continuous N₂-gas flow through sample chamber, mounted on horizontal spectrometer axis (details). Temperature Range / Coolant
• 80 - 500 K
• Coolant: liquid N₂
• Recommended Sample Holder and Maximum Sample Size: Special design for glass bulbs, max. bulb diameter 35 mm, cylindrical shaft 8 mm diameter, adjustable sample stick length. Drawing.

  ³⁾

Note: CCR and New Chemistry Cryostat use the same vacuum chamber. Changing cryostats is easy.

Temperature Control

• Conductus LTC-21 for CCR, New Chemistry liq.N₂ and Janis ⁴He: Serial Nr. 300394, GPIB 13, in rack on platform in the area. The Heater of this LTC is used to control the 10K-CCR-Cryostat in single-loop mode or the Janis ⁴He-Cryostat or the Chemistry-Cryostat in two-loop mode using the analog output and a Gossen/Konstanter DC-power supply in addition as the second loop. Click on the cryostat name to see the PID and gas flow tables for CCR, New Chemistry and Janis.
• OXFORD ITC 4 and ITC 5 for Oxford ³He.
• Conductus LTC-21 for additional sensors on the sample holder of the Oxford Heliox insert: Serial Nr. 300059, GPIB 14, in rack on platform in the area. It is used in Monitor mode only.

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Check-List for GPD Installation

click here.

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Electronics / Data Acquisition

• NIM Electronics Logic Diagram version 2008 with Ortec pTA-clock (the LeCroy TDC has been removed!)
• A manual for the MIDAS acquisition software and on DELTAT are now also available

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Computers


• The Experiment Console (PC6011 running Scientific Linux) is located in Studio A. You can start the programm DELTAT on this machine.
• A Front-End Windows-PC (PC4684) for the data acquisition system using the Ortec pTA-clock is located in the electronics compartment of Studio A.
• A Back-End Linux-PC (PSW404) for the data acquisition system located in WHGA.

• A Linux-PC (PC4247) for local access to the AFS-files by PSI-software (local account name: l_musr_gpd, ask instrument scientist for password), e.g. LOOK_MUSR.

• A Low-cost Linux-PC (PC4807) for general use (same account name and password as PC4247).

• Client-PC using Windows-XP for beam line and area servers: PC284 in Studio A (Infos on Control System for Secondary Beam Lines). Please don't use this PC for other applications.

• Beam line server-PC: PC202 on 2^nd floor, galery east.

• A Windows-PC used for controlling of the Variox/Heliox is located on the platform in the area (PC3375).
• A number of different devices (e.g. temperature controllers, Gossen magnet power supply, etc.) are controlled by the Deltat slow control 'front ends' Modify Devices or Exp. Magnets by means of GPIB bus or RS-232 serial line.
  • Two Agilent LAN/GPIB Gateways are used:
    • One in Studio A (psgs009) for the Gossen magnet power supply and
    • the other one in the area (psgs004) for temperature controllers and the gas flow control etc.
  • A Lantronix ETS8PS 8-channel RS-232 terminal server (psts220) located in the yellow rack in the area is used to control the stepper motor drive controller.
• A 10Base-T micro hub (MR820TR) is used to talk to the LAN/GPIB Gateway psgs004 and to PC3375 in the area.
• Two switch boxes (Nortel Networks type BayStack 450-24T) connect all PCs, servers and gateways to the ETHERNET:
  • BwehaE09 in Studio A and
  • BwehaE10 in the area (bottom of yellow rack).

Printers

Printing from Unix, Linux and VMS is now performed using the CUPS system. 

From the VAX workstation, to print ASCII files and Postscript files the command psprint should be used.

From UNIX/Linux-Cluster you can either use the glp command and choose the appropriate printer (e.g. WEHA_E5_2 located in the blue cabin near experimental area πE5).

For more information on CUPS, just look here. 

To print from a Windows Laptop, one should just install the corresponding printer:

Click the Start button and choose Run... option.
When prompted for a command just type \\PRINT00
On the list choose the corresponding printer (e.g. WEHA_E5_2).
Right click and choose Install...

For more information, look here.

Finally one can also print local files directly from a browser using this link.