Nuclear Engineering ETDs

Dal H. jensen

Publication Date

5-2-1975

Abstract

ABSTRACT

A new approach to the measurement of the neutron yield of low intensity (~ 2 x 10 neutrons/pulse) 0-0 neutron generators in a single pulse is described. A cylindrical (20.32 cm radius by 20.32 cm height) scin­tillator of Pilot-Bis optically coupled to a Phillips 57AVP photomulti­plier with a 20 cm diameter photocathode. The light pulse resulting from the neutron burst is fed into a voltage integrator calibrated in neutrons/ count.

The initial calibration of the stable neutron generator used in the scintillator calibration was performed using a silver activation detector (PT-502) designed by LASL. The data obtained for the distance curve in this work was least squares fit to with the corresponding LASL data and matched with a maximum error of 4.2%. The neutron generator was determined to have a yield of 3.66 x 105 neutrons/pulse with an accuracy of± 8.7% resulting from the internal error analysis. The total error, which includes the absolute calibration error from LASL, was 17.3%.

The scintillation detector at 1800 volts and terminated in 50 ohms was determined to have a sensitivity of 45.3 ± 8.2 neutrons/count using the voltage integrator with a sensitivity of 200 counts/volt-µsec. This corresponds to a detector sensitivity of 452.5 ± 82.1 neutrons/ma-µsec. The total error for the detector calibration was estimated to be± 18.1%. A simulation of the detector performed using two different computer codes demonstrated that a Monte Carlo code allowing multiple scattering within the detector was able to predict the efficiency better than an analytical model which assumed only two interactions/neutron. An exten­sion of the detector calibration to other energies was discussed.

Document Type

Thesis

Language

English

Degree Name

Nuclear Engineering

Level of Degree

Masters

Department Name

Nuclear Engineering

First Committee Member (Chair)

D. M. Lucoff

Second Committee Member

Robert L Long

Third Committee Member

Illegible

Fourth Committee Member

Illegible

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