Electron wire chambers ePC1, ePC2

As mentioned above the geometry of the hydrogen vessel is designed so that existing wire chambers from PSI can be reused, which have been built for the Sindrum I and the -conversion experiment. For ePC1 Sindrum chamber 3 (spare chamber, not used thus far) and for ePC2 Sindrum chamber 5 will be used. The chamber parameters are given in table 5. Cathode strips of 0.03 aluminum coating on 25  thick Kapton foil are glued on the self supporting inner and outer cylinders made of Rohacell 51 foam. Their stereo angle towards the axial anode direction is , respectively.

Table 5: Chamber characteristics

	ePC1	ePC2
active length(mm)	580	800
diameter anodes (mm)	384	640
half gap (mm)	4	4
pitch anode wires(mm)	2.3	2.0
width cathode strip(mm)	4.44	4.44
# anodes	512	1024
#strips (inner)	188	316
#strips(outer)	196	324
thickness inner wall(mm)	1.5	0.45
thickness outer wall (mm)	1.5	0.20
operating voltage (V)	2750	2950
diameter anode wires W(Au)( )	20	20

Thus far, the chambers were operated with Ar(49.9%)-Ethane(49.9%)-Freon(0.2%) with muon fluxes of . This mixture shortened the active layer to 2mm, allowed a moderate gas gain of and extended the lifetime of the chambers. As our anticipated flux is 100 times smaller, we are considering the use of higher gain mixtures, like magic gas.