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NSLS ESH Highlight #7

Chipmunks - A Way to Monitor Radiation

Date: November 27, 1996 (Rev. 12/13/2001)
Editor: N. Gmür, W. Thomlinson

What is a “Chipmunk”?

A Chipmunk is a radiation monitor which determines local dose due to gamma and neutron radiation.

How Are Chipmunks Used at the NSLS, SDL and the ATF?

Chipmunks are placed in locations around Building 725, 729 and 820 where it is deemed advisable to monitor short and long term radiation trends and patterns. This includes areas around the NSLS Linac, booster ring, VUV and X-ray rings, beamline front ends, and certain 2nd floor offices; around the SDL accelerator; the ATF Experimental Hall, gun hutch and laser rooms. The output of the Chipmunks currently in place is accumulated in history files and analyzed as needed. Their alarms are also used to warn people in their vicinity that radiation levels are elevated.

How to Recognize a Chipmunk

Each Chipmunk has an analogue dial on the front indicating dose in millirems per hour. A series of three colored lights are associated with three dose ranges:

Light Color
Dose (mRem/Hr.)
<1.0 - 2.5
2.5 - 20

Note: above 40 mRem/Hr. the chipmunk alarm will sound continuously. Due to time-averaging, the chipmunk alarm lasts longer than the actual radiation event itself.

(Please ignore “Occupancy in Hrs./Day” on the chipmunk shown above left)

What to Do if a Chipmunk Gives Off an Alarm in Your Area?

Under normal conditions Chipmunks will give off occasional chirps and show a green light under background radiation conditions. If the rate of chirps increases and you see that either the yellow or red light is illuminated, do the following:

  1. Move away from the vicinity of the Chipmunk and the probable source of radiation.
  2. Telephone the Control Room (NSLS = x2550; SDL = x5350, ATF = x2306) and inform the staff that a Chipmunk in your area is giving off an alarm. Specify the exact location of that Chipmunk and, if you can see it from your location, indicate the level of the alarm (yellow or red).


Call the NSLS Safety Officer, x5431.