Wojciech Gajewski
University of California Irvine

This is a description of the picture, which shows the MUON RANGER setup.

The picture and this description was sent to Dr. Nishikawa on Feb-14-1995.

The scale in the picture is in meters. The elements of the setup are as follow:

  1. The target:
    The front size covers 1 mrad so its radius depends on the distance from the beam production target. In the example drawn in the picture it was assumed that this distance is 500m. The target is built from 15-20 cm containers filled with water. The total water weight is 1.2 tons. Between the containers there are tracking devices described further in this text. The total target length is 2 m. The target is surrounded also with tracking devices.
  2. The muon ranger:
    Muon momenta are measured by ranging them out in three sections of steel plates. The two outside sections are rotated by 30 deg. There is 22 steel plates, each 10 cm thick, in each section. The size of the plates in the outside sections is 2 by 2 m, in the central section they are 2 m tall but they have to be cut to proper transverse dimension. The longest of them has to be about 3.3 m wide. Between the plates there are tracking devices (x and y) in the first few sections, further down they can be replaced by liquid scintillator counters (if cheaper). 2.2 m of steel is sufficient to stop 2.5 GeV/c muons. It is the highest momentum at 30 deg angle. For smaller angles there are muons with momenta up to 4 GeV/c and they are ranged out in the water tank.
  3. Time of flight system:
    In the gap between the target and the steel plates, at least 50-60cm wide, there is a set of two scintillator counters which allows us to distinguish the muons going from the target to steel from those which go from steel to the target.
  4. Triggering:
    The system is activated by a gate associated with the beam for a duration of the spill length (2-3 usec). The hits in the tracking devices are latched during that gate. The TDCs in the time of flight system are also started by the beginning of the gate and stopped by signal from the scintillators. They have to have respectively long dynamic range. After the beam spill the data are read and analyzed, non empty triggers are being saved. The same is with the triggering of the water tank.
  5. The acceptance:
    The acceptance of the MUON RANGER has to be modeled and the weights to every event have to be applied. As long as it is pure geometry it should not be a problem.
  6. Support:
    The MUON RANGER is build on a floor on the level of the bottom of the water tank. Since the total mass of the steel is about 190 tons no additional reinforcement of the floor seems to be necessary. The steel plates and the target have to be mounted on frames which are about 2 m tall. This is the same way the Fermilab E815 calorimeter is constructed.