Models SRJ-7 and HRJ-7 Juno Survey Meters

Bulletin No. 180
INSTRUMENTATION FOR NUCLEAR RESEARCH
SURVEY METER, Models SRJ-7 and HRJ-7
Incorporating design features which permit
e !ration under high humidity conditions
APPLICATION. The Juno Survey Metei, is a portable
instrument for measuring the intensity of, and
discriminating between alpha, beta, and gamma radiation.
It is used to protect personnel from the dangei, of
over-exposure to radiation from radioactive mateijals
or X-rays. While primarily intended for inspection of
flat surfaces, the instrument is suitable for most uses
where a high degree of accuracy is desii.ed.
The T/A Juno is available in two models: SRJ-7
(standard range) for all normal applications; and
HRJ-7 (high range) for use whe1.e exceptionally high
intensity radiation is likely to be encountered. Both
models meet A.E.C. specifications.
Models SRJ-7 and HRJ-7 are improved veisions of the
original Hanford instrument. The high impedance circuit
switch box includes a desiccant cartridge and is
sealed with gaskets. These design impi.ovements insure
high efficiency pei.formance under adverse humidity
conditions.
DESCRIPTION: The instrument comprises an
ionization chamber, an electrometer ciiruit, absorption
filters for the rejection of either alpha or beta particles,
suitable batteries mounted in a i,emovable power pack,
and an indicating meter. The unit is battery operated
and is self-contained. To easily identify the High Range
Juno, its knobs and meter dials are finished in brilliant
red.
The ionization chamber has a volume of approximately
27 cubic inches. All surfaces within the chamber are coated with aquadag.
The chamber is covered by a screen of .0003” (approximately 0.45 mg/cm2)
rubber hydrochloride film. The alpha screen is within 7/16” of any flat
surface on which the instrument may be placed, and is easily replaced by
simply removing the bottom plate and two retaining screws.
Two absorbers are provided to reject either alpha or beta
radiation. These are readily moved in and out of position by means
of sliding tabs fitted in rails which form part of
the handle. The tab marked “G:’ with a square
end, operates the absoi.ber which rejects alpha
and beta, thus permitting a reading of gamma
only. The tab marked ‘‘By with a rounded end,
operates the absorber which rejects alpha, permitting
a reading of beta and gamma. The total
of all three types of radiation is read, when both
tabs are in “open” position.
The high quality microammeter, which is calibrated
in milliroentgens per hour for gamma radiation,
has a large easy-to-read face and is mounted
in position to permit excellent visibility. Ratteyy
life is approximately 800 hours in normal intermittent
use. An easily removable battery pack,
with simple positive contacts, assures trouble-free
operation over long periods of service.
I
ALPHA WINDOW
ALPHA ABSORBER
BETA ABSORBER
Td
1 1 140 WEST PROVIDENCIA AVENUE BURBANK, CALIFORNIA
TE C H N I CAL ASSOC I ATE S
3M-4/61 (Rev.)
Printed in U.S.A.