Choice of detectors

Several detector types fulfil these physics requirements. In our collaboration there are 2 groups (JINR-Dubna and IHEP-Protvino) that have been previously involved in the construction of muon detectors.

• The Dubna expertise is in the field of Plastic Iarocci tubes. The workshop produced more than 25000 tubes for the hadron calorimeter of the DELPHI experiment. A detailed description of the workshop and the results of the mass production can be found in [24].

  Furthermore Dubna Iarocci tubes are used as muon surround chambers in DELPHI [25] and an agreement with the D0 collaboration at Fermilab to produce 6000 Iarocci tubes was signed recently.

  Typical characteristics of the PIT are the following:

  • The maximum drift time is about 50 ns (for fast gas used in the D0 tubes), or about 100 ns (for slow mixture used in the DELPHI tubes) (see Fig.1).

     
    Figure 3.7: Measured time spectrum of PIT used in the DELPHI Surround Muon Chamber.
    

    [1]This figure replaces the wrongly labeled figure 5.15 in the proposal.

  • The typical spatial resolution of a tube is better than 200-300 , when read via TDC's. The spatial resolution of a muon station is limited by the mechanical precision and is about 1 mm. However, for our case even a standard readout of the PIT is adequate, providing a resolution of 1cm/ and 2cm/ for the wire and strip readout, respectively.
  • Aging tests have been done for D0 prototypes and no effects up to a dose of 1.67 C/cm were found. At a rate of 200 10 years of operation give a total charge of the order of 0.1 C/cm. So no significant aging effects are expected.

  The construction of the 6000 tubes for the D0 experiment is foreseen for 1997. The preparation work and necessary R&D will be financed by Fermilab and JINR. The 1200 tubes for COMPASS could be produced in 1998 as an extension of the activity connected with the Fermilab contract. The average capacity of the workshop is 50 tubes per day and a total of 3 months is needed for the production and testing of all the tubes. The tubes including frontend electronics would be financed by Dubna. The corresponding cost estimate is 310 kCHF.

• IHEP Protvino has experience in the production of drift tubes. The same type of drift tubes proposed for COMPASS is already used in the SAMUS muon spectrometer of the D0 experiment at Fermilab [26]. In total, the workshop produced 6000 drift tubes. The drift tube technology is proven to work well and reliably ensuring high enough spatial resolution. No aging problem is expected to be encountered. Part of the material for the production is already available in Protvino and the workshop is capable of producing the 3000 tubes for COMPASS by the year 1998 (the average capacity of the workshop is 30-50 tubes per day).

  IHEP would be responsible for construction and production of both tubes and frontend electronics (amplifiers & shapers), equipped with low voltage supplies. The corresponding cost estimate is about 170 kCHF.

The two different detector types for the muon detection in COMPASS meet the requirements of the experiment. The share of responsibilities for the subdetectors between the two groups follows the expertise of the institutes.