Memorandum from Arthur Waltner to Clifford K. Beck
Typescript
1 p.
April 14, 1951
MurNBbeta041451



NCSC-17

April 14, 1951

TO: Clifford K. Beck
FROM: Arthur Waltner
SUBJECT: Beta Particle Transmission for Aluminum Windows

The range-energy relation for beta particles up to 3 Mev is given by the
relations

In the above relations, R is expressed in gm/cm² and E in Mev. The calculated
end-point range of a 1 Mev beta spectrum is thus 0.41 gm/cm² which is equivalent
to 0.15 cm of Al.

The percent transmission of the beta particles of Bi210 through a series of Al
absorbers as obtained in our laboratories is tabulated below.a (Maximum energy
of Bi210 [beta] particles - 1.17 Mev.)

TABLE I
Absorber
mg/cm²
Thickness (Al)
mm
% Transmission
00100
200.0774
300.1163
400.1453
600.2240
800.2929
1000.3722
1200.4416
1400.5212
1500.567.2
1800.676.4
2000.744.7
2400.892.5
2801.031.4
3201.19.86

Thin wall GM tubes are produced commercially with wall thicknesses of 30 mg/cm²
in Al, glass, or stainless steel, some of which are designed as dipping counters.
For the RaE (Bi210) spectrum this represents about 63% transmission. It thus
seems feasible to design stack and coolant monitors which will be sufficiently
sensitive to beta particles, regardless of the choice of the detecting element.

CC: Reactor Committee


Notes:

adata gathered by W. T. Withers