Physics and Engineering of Radiation Detection

444 Chapter 7. Position Sensitive Detection and Imaging

Cathode Plane

Anode Wire

Electric

Field Lines

Cathode Plane

Figure 7.2.3: Electric lines of force inside the active volume of

a multiwire proportional chamber.

of many single proportional counters therefore the pulse profile recorded from each
of the wires is similar to the one obtained from a conventional single wire cylindrical
proportional counter. The time profile of the pulse is mainly dictated by the time
constant of the circuit as shown in Fig.7.2.4.

τ 1

τ 2

τ 3

τ 3 >>τ 2 τ 1

Pu

lse

H

ei

gh

t

Time

Figure 7.2.4: Typical pulse time

profile recorded from a single anode

wire of a multiwire proportional

counter. Note that the shape of the

pulse depends on the time constant

τof the circuit.

The MWPC described above can give only one dimensional position resolution.
To obtain two dimensional event identification, one generally uses two such detec-
tors with wires perpendicular to each other. A time coincidence unit can then tag
the events in the two chambers as being from the same particle. An even higher