Foil Activation Method Research Articles

A method for measuring neutron spectra in a stopping pion field

A multiple foil activation method for measuring the neutron energy spectrum in a stopped negative pion field is described. A knowledge of this spectrum is a vital prerequisite to calculations of dose and LET distributions at any point in the field. The method is simple enough to be used for routine dosimetry of clinical pion biomedical beams.

252Cf neutron irradiation facilities

An activation facility has been designed for the accomodation and safe-handling of up to 50 mg of 252Cf neutron source. The absolute values of thermal, epithermal and fast neutron fluxes were determined by the foil activation method using In, Dy, Au, Al and Fe detectors, and compared with other experimental results and theoretical estimations. The Maxwellian temperature and average energy of 252Cf neutron spectrum have been determined.

A precise 14 MeV neutron detector

A 14 MeV neutron detector is proposed which is capable of excellent discrimination against lower energy neutrons, gamma and beta rays. It is based on the detection with a ZnS scintillator of the alpha particles resulting from the 12C(n,n′)3α reaction in a carbon foil. The detector agrees within 1% with the standard copper foil activation method and shows negligible response to interfering radiations, excellent linearity, no aging effects and prompt response. Hence it can be utilized as the sensor for a servomechanism to control the neutron flux in 14 MeV neutron generators.

箔放射化法による核分裂反応率の測定

箔放射化法による核分裂反応率の測定

A study of atmospheric neutrons by the resonance detector method

The possibilities and the conditions of using resonance detectors for investigation of slow neutrons in the atmosphere are discussed. The epithermal neutron fluxes from the lower hemisphere were measured by means of the indium foil activation method in June 1966 at the geomagnetic latitude 47°. Assuming the epithermal atmospheric neutron spectrum to be Φ(E) = Φ0/E and expressing the neutron energy in eV, we obtain the following values of Φ0 (neutron cm−2 s−1) from our measurements: 0.078 ± 0.019 (at a depth x = 40 g cm−2), 0.049 ± 0.015 (x = 22 g cm−2), 0.023 ± 0.010 (x = 8 g cm−2). It is pointed out that resonance detectors can be used to study the spectra of epithermal neutrons in nonequilibrium atmospheric layers.

Corrections in the gold foil activation method for determination of neutron beam density

A finite foil thickness and deviation in the cross section from the 1 ν law imply corrections in the determination of neutron beam densities by means of foil activation. These corrections, which depend on the neutron velocity distribution, have been examined in general and are given in a specific example for a reactor beam transmitted through a 30 cm Bi filter. The effective cross section differs 0.5% from the capture cross section at 2200 m/s. For a 20 mg/cm 2 Au foil the correction for beam attenuation and hardening through the foil is 0.7% and the activity correction is 1.5%.