SµS • Swiss Muon Source

General Specifications

• Location: area piE1.
  
• Positive muons, standard momentum 28 MeV/c (other momenta possible).
  
• Degree of polarization >95%.
  
• Direction of spin ~180° with respect to muon momentum (longitudinal polarization; spin rotator for transverse polarization under construction).
  
• Positron detectors: 2 longitudinal, 2 transverse.
  

Detector Arrangement

• A muon detector (M).
• Four positrons detectors (with respect to the beam direction) :
  Forward (F),
  Backward (B),
  Left (L),
  Right (R).
• A backward veto detector (B_veto), consisting of a hollow scintillator pyramid with a 7x7 mm hole facing the M counter.
  The purpose of B_veto is to collimate the muon beam to a 7x7 mm spot and to reject muons (and their decay positrons) missing the aperture ("active collimation").
  
• A cup-shaped forward veto detector (F_veto) for use with samples that do not cover the entire beam spot.
  Its purpose is to reject muons (and their decay positrons) that have missed the sample.
  When the sample/holder assembly stops all muons, the F_veto signal may be added to the F signal to increase the forward solid angle.
  

Available drawings of the detector arrangement:

• GIF :
  Horizontal cross section (15 kB).
• PostScript:
  Horizontal cross section (160 kB).

Sample Environment

Cryostat

• Type: Oxford Variox (top loading, sample in He-4 exchange gas).
• Temperature range: 1.6-300 K.
• Sample holders: Two sample sticks are available.
• Sample rotation: Remote-controlled rotation of the sample stick for orientation-dependent measurements can be made available on request. Please contact the instrument scientist.
• Reference Manual: is available (but more up-to-date information is available in the QUICK REFERENCE MANUAL).
• Liquid He is supplied in two 100 litre dewars. While one dewar is in use, the second one is being refilled by PSI staff at the filling station in the experimental hall (west gallery). Therefore it is vital that the empty dewar is immediately brought back to the filling station and not left in the area. Contact the instrument scientist for help. The dewars should not be emptied completely. Leave about 10% level.

         In preparation:  Oxford Heliox He3 insert for the temperature range 0.3 -- 300 K (contact the instrument scientist).

Sample Size and Recommended Sample Mount

• Sample chamber (Variox): Free diameter 31 mm, distance from bottom of sample chamber to center of beam spot is 41 mm.  A sample of 10 mm diameter and a thickness of 0.2 g/cm^2 at the correct position will stop the majority of the incoming muons.
• Drawings of the sample region (Variox with Heliox insert) are available here.
• Sample holder: Drawings of the sample holders recommended are available (standard / modular).
• Please note:
  • The users are expected to bring their own sample holders and to 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.

Temperature Control (see QUICK REFERENCE MANUAL)

 Temperature Sensor History  is here.

Magnetic Fields

• Main field (WEU): 0-0.49 T parallel to the beam (the coil design allows 0.8 T when an appropriate power supply becomes available).
  
• Auxillary field (WEV): 0-15 mT perpendicular to the beam.
• Earth-field compensation: Two pairs of coils for the components perpendicular to the beam (horizontal and vertical) and one pair for the component parallel to the beam (longitudinal). Compensation is usually better than 0.001 mT for all components.
   

Electronics / Data Aquisition

Data Format and Storage

The users are responsible to store in a safe place their own data. Every week a backup of the data is performed in the PSI Archive system and the specific muSR ftp-server (see here for more information). 
You are strongly adviced to retrieve your data ("bin"-format) using our new ftp-server.

A manual for the acquisition software deltat is available in HTML fomat or in PDF format

Logic Diagram

The new TDC electronics is characterized by a logic performed exclusively at the software level. A manual is available in HTML fomat or in PDF format. The electronic logic is similar to the one of the GPS instrument (see Manual of GPS).

Computers

The area is equipped with a Experiment Console (running Scientific Linux) pc8533. The µSR data acquisition system hardware consists of this console and a Linux back-end server (psw403) located in the computing building (Hauptgebäude). This back-end is connected to a front-end PC running Linux and controlling the VME electronics.
A number of different devices (temperature controlers, magnetic field power supplies, etc...) are used for the slow control of the experiment.
These devices are mainly controlled via GPIB (IEEE-488) bus or RS-232 serial line.

• GPIB :
  The GPIB devices are controlled through a Agilent LAN/GPIB Gateways (E2050A and the newest E5810A).
  
• RS-232 :
  The RS-232 devices are controlled through either a Agilent LAN/GPIB Gateways (E5810A) which supports one RS-232 line, or a Lantronix ETS8PS 8-channel RS232 terminal server

The acquisition software deltat is based entirely on the DAQ software package MIDAS.

A Linux Workstation is also available and can be used through a usual AFS account or a local account (ask the instrument scientist for information). From this machine, one can connect also to the Linux cluster. 

The secondary beam-line control system controlling beam-line elements (magnets, slit systems, etc.) between the target station and the experiment consists of a CAMAC crate containing the interfaces and modules needed for the beam line, a server PC (connected to the CAMAC crate) and an area PC.
Area PC: Intel processor running under Windows XP.
 

Printers

Information about how to print at PSI is available here.

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

From UNIX/Linux-Cluster you can either use the glp command and choose the appropriate printer (WEHA_PIE_1).
You can also set the environment variable PRINTER to be equal to the name of your printer, and use the lpr command.

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 \\winprintw
If a account and password is requested, just use "guest" as account and disregard the password by pressing ENTER
On the list choose the corresponding printer (WEHA_PIE_1).
Right click and choose Install...

For more information, look here.

From a Linux Laptop you can install a CUPS client. Look here for more information.

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