Expt. 03005 postcalibration analysis
The efficiency curves shown below were measured 28 April 2004, after NSCL Expt. 03005.
Twelve 32-segment Ge detectors from the MSU SeGA array were
placed in two rings around the DSSD implantation detector.
Germanium array geometry
The germanium detector geometries as entered into the Monte-Carlo N-Particle (MCNP)
transport program are shown given in the links below. The positive X direction
is downstream of the DSSD implantation detector, the positive Y direction corresponds
to the South direction in the N3 vault.
Photos of the Ge detector arrangement can be found at the following link:
groups.nscl.msu.edu/beta/BetaDecay/calorimeter.html
Individual detector efficiencies
Source: SRM-4275-C69 for absolute calibration
Source: Co-56 prepared at FSU for relative calibration to 3.2 MeV
Data were collected using both an MCA and the NSCL Spectrodaq
system for each source separately. Independent measurements were made
for each detector using the SRM-4275-C69 mixed source. Simultaneous measurements
were made for all 12 detectors with the Co-56 source.
Array peak efficiency
The peak efficiency for the total 12-detector array is given below. The
data were fitted to an MCNP simulation for a point-source geometry,
and the overall agreement between 150 keV and 3.5 MeV is excellent.
The posted equation is the result of a
trendline fit to the MCNP simulation points (log Efficiency vs. log Energy)
using a fifth-order polynomial function.
Ge array peak efficiency curve
(original)
Ge array peak efficiency curve
(with simulation to 40 keV)
MCNP Simulation File
The MCNP source code to calculate the efficiency curve
for the point source geometry can be downloaded from the link below. To save
the file on your local disk, click on the link with the right mouse button
and select "Save Target As..."
MCNP file 01015P.i
updated 14jul04 by pfm
