DOLLY: Multi Purpose Surface-Muon Instrument

  • Location: area piE1.
  • Positive muons, standard momentum 28 MeV/c (other momenta possible).
  • Degree of polarization >95%.
  • Direction of spin ~8-45° with respect to beam axis (depending on the mode of the spin-rotator).
  • Positron detectors: 2 longitudinal, 2 transverse.

  • 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:


  • 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 test operation: Oxford Heliox He3 insert for the temperature range down to 0.25 K (see a dedicated HELIOX QUICK REFERENCE MANUAL).

  • 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 Sensor History is here.

Magnetic Fields

  • Main field (WEU): 0-0.8 T parallel to the beam.
  • Main field (WEUL): 0-50 mT parallel to the beam (high precision over restricted range).
  • 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.

Data Format and Storage

Users are responsible for storing their own data in a safe place. Every week a data backup is performed in the PSI archive system and in the specific μSR FTP-server. You are strongly advised to retrieve your own data (in native "root" format, or exported to "bin") from the web page

A manual for the data-acquisition software deltat is available 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 in PDF format. The electronic logic is similar to the one of the GPS instrument (see Manual of GPS).

The old PTA logic diagram is available as pdf-file (780 kB).

The area is equipped with an Experiment Console (running Scientific Linux) pc8533. The µSR data acquisition system consists of this console, a Linux back-end server (psw418) located in the computing building (Hauptgebäude) and a front-end PC (PC12022) running Linux controlling the VME electronics. A number of different devices (temperature controllers, magnetic-field power supplies, etc.) are used for the slow control of the experiment.

These devices are mainly accessed via GPIB (IEEE-488) bus, RS-232 serial line, TCP port, or EPICS Process Variables.

  • GPIB: The GPIB devices are accessed through Agilent LAN/GPIB Gateways E5810A.
  • RS-232: The RS-232 devices are controlled through RS-232 terminal servers. Moxa NPort 5110 or NPort 5150 1-channel, Lantronix ETS8PS 8-channel, Moxa NPort 5650 8-channel or Lantronix EDS16PR 16-channel RS232 terminal server.

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

A Linux workstation (pc13369) is also available for data analysis 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 HIPA secondary beam-line control system controls the beam-line elements (magnets, slit systems, etc.) between the target and the experiment. The area is equipped with an EPICS Console (hipa-pie1-02) to set the EPICS Process Variables of the beam-line elements, to optimize beam settings, and for diagnosis.


Information about how to print at PSI is available here (reachable only through the intranet at PSI).

Printing from Unix and Linux is performed using the CUPS system. The nearest printer located in the SinQ Hall is WNHA_151_1. The Xerox color printer may be found on the 1th floor next to the Zebra cabin which is close to the BOA and HRPT experiment area. Another printer located in the Experimental Hall is in the blue cabin near the piE5 area and has the name: weha_e5_2.

From UNIX/Linux-Cluster you can either use the glp command and choose the appropriate printer (WEHA_EG_2). 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_EG_2). Right click and choose Install...