SERL _ MRP
06 December, 2004
The Schaefer Environmental Radiation Laboratory (SERL) is a cluster of a rooms within
the Physics Department that contain instruments for measuring radon, environmental
sampling, and spectroscopy systems for alpha and gamma radiation. This facility is
dedicated to the spirit of Thomas O. Schaefer, SJU '81. Tom's
pioneering senior thesis work on the gamma spectra of outdoor radioactive particulates
opened an era of collaborative research on environmental radiation by students and Dr.Steck . Employing hard work, dedication, and initiative, Tom
built both a useful detection system and a tradition. Tom, a Marine pilot, died in a
military aircraft accident in 1984. This facility was dedicated to his memory in 1985.
Most of the research activity of the Minnesota Radon Project (MRP) is conducted in this
Since we're physicists, we tend to enjoy developing and using
instruments that are sometimes more sophisticated than needed for "typical"
radon measurements. We have some sophisticated alpha and gamma spectrometers for low level
radioanalytic analysis. But we also have radiation detection systems that are inexpensive
and low tech, like track registration radon and radon progeny monitors (see Getting Tested).
Radon and Progeny Concentrations:
- Radon monitors :
- Durridge RAD7 (2) with bubbler for Radon in Water
- Pylon AB5+PFT (4)
- 4 Ludlum 2200s + 218 & 182 photomultiplier assemblies - computer interfaced
- 32 ZnS flow through scintillation chambers ranging in volume from 35 to 600 mL.
We maintain a calibration of these monitors through the annual intercomparison
exercises conducted by calibrated government and private radon chambers.
- Radon Progeny monitors:
- SARAD EQF 3120
- Thomson-Neilsen TN-2
- Pylon WLx.
- 5 scintillation based WL counters
- Radon chambers:
- A "bedroom sized" exposure room (30 m^3) with controllable air exchange,
aerosols, humidity, and radon concentration. Radon concentrations up to
150 pCi/L with monitoring for
radon, radon progeny ( cluster and attached modes), ventilation, T,
Rh, air velocity, pressure, ion density
- A 0.5 m^3 chamber for concentrations from 20 to 3000 pCi/L and a 0.025m^3 chamber that
has achieved concentrations up to 500,000 pCi/L.
- Surface alpha activity:
- 15 semiconductor CAM diodes,
from 900 mm^2 to 2000mm^2,
- Four PIPS diodes from 300 mm^2 to 900 mm^2
- Canberra alpha spectroscopy vacuum chamber
- Power supply
- Portable PC based MCAs (Aptec) (3 systems)
- 6 Ludlum 2220+43-1 ZnS.
- Surface gamma survey instruments:
- Ortec HpGe-55195 Gamma cage in Canberra 717, 2" Pb shield connected to Aptec PC MCA
- Odyssey Bicron 3MT3/3 NaI in Gamma Products 3" Pb shield connected to portable
Aptec PC MCA Ludlum model 12S microR meter (for remote surveying)
- Computer-interfaced GPS system for automapping
- Integrating radon and progeny monitors:
- Alpha Track radon Detectors (ATDs): 2 indoor and 1 outdoor models
- EPERM system
- Retrospective Reconstruction Detector (RRDs)
Radon transport in soil characterization:
- Field permeability:
- Our permeometer is a 1 m long, 8mm diameter tube coupled to an electronically timed,
pressure monitored 16 L manifold. The manifold is evacuated to approximately 50 kPa. Then
a 2 to 5 point pressure decay curve is measured. The linear least squares fit to the
logarithm of the pressure decay curve produces a estimate for the permeability.
- In the lab we have measured the diffusivity of packed soil samples (cylindrical; 10 cm
long x 6 cm diameter) be fitting the time dependence of a scintillation chamber fitted
with the soil column which serves as a diffusive leak.. In the field we estimate the
soil's diffusivity from the ratio of the radon gas concentration at 0.3 m to the radon gas
concentration at 1 m.
- PC ArcInfo+ArcView with address geocoding
- SURFER countouring software+Mapviewer
- Calcomp digitizing table 36"x48"
- Color scanners and printers
Back to the MRP
Last revised :
06 December, 2004
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