Photoneutron spectrometry by time of flight

doi:10.1016/0029-554X(65)90042-X

Nuclear Instruments and Methods

Volume 33, Issue 2, 2 March 1965, Pages 199-212

https://doi.org/10.1016/0029-554X(65)90042-X Get rights and content

Abstract

A general account is given of the methods of photoneutron spectrometry using nanosecond time of flight techniques and a pulsed electron source. Included are some details of the Massachusetts Institute of Technology electron linac facility with emphasis on the experimental geometry, the electron gun, the neutrons detectors and timing and logic circuitry. Problems associated with the gamma flash, the specific bremsstrahlung associated contributions to timing accuracy and resolution, optimum pulse width and neutron detection efficiency are discussed. By means of a specific example, C¹³(γ,n)C¹², the reduction of data to differential cross section is elaborated. The sources and magnitudes of backgrounds are reviewed in this example.

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Cited by (8)

The photoneutron cross section in 13C
1976, Nuclear Physics, Section A
The photoneutron cross section in ¹³C was measured using bremsstrahlung from an electron synchrotron operated in energy sweeping mode. Neutrons were detected by a multi-BF₃-counter detection system. Decorrelated cross-section ordinates were calculated directly using a modified Leiss-Penfold analysis. The cross section from threshold to 25 MeV shows detailed structure, some nine maxima, in agreement with recent continuum shell-model calculations.
High-energy levels in 13N (II)
1976, Nuclear Physics, Section A
The reaction ¹²C(p, γ)¹³N has been studied over the energy range 9 <E_p <14 MeV. New structure is established around E_x = 20 MeV in the giant dipole resonance of ¹³N. The interference dips at E_x = 11.74 MeV and at 14.04 MeV are confirmed as $32^{+}$ levels interfering with a pygmy resonance which has a predominantly $32^{+}$ strength. Total cross-section yield curves for the 12.71 and 15.11 MeV inelastic γ-rays have been obtained up to E_p = 24 MeV, and new structure is observed.
Time-of-flight scattering spectroscopy
1976, Advances in Atomic and Molecular Physics
This chapter discusses the time-of-flight (TOF) scattering spectroscopy. TOF spectroscopy consists of many groups, each of which is only concerned with one type of particle and a limited energy range. Measurement of the flight time t of a single particle traversing a well-defined flight path of length L yields the particle velocity υ = L/t. The compilation of flight-time values measured for a great number of beam particles gives a flight-time distribution from which the velocity or the energy distribution can be calculated. The time at which the particle enters the flight path is defined by the action of a beam gate and marked by an electronic gate signal; the second time-mark is given by the electronic signal from a fast-response particle detector at the end of the flight path. In a special form of singleshot operation, TOF measurements are performed on continuous particle beams without the use of a beam gate; the particle to be timed provides a signal when it enters the flight path, for example, by penetrating a transmission detector. This is called single-particle zero-time pick off. TOF scattering spectroscopy is applied in many different fields. For spectroscopy with high energy neutrons, it is the only high-resolution method available. The two greatest advantages of TOF spectroscopy are its conceptual simplicity and its excellent compatibility with computerization.
A facility for fast neutron time of flight experiments
1973, Nuclear Instruments and Methods
Photoneutrons from 13C at photon energies up to 14 MeV
1970, Nuclear Physics, Section A
The photoneutron yield of ¹³C was measured as a function of the maximum bremsstrahlung energy up to 14.5 MeV. The cross section for the ¹³C(γ, n)¹²C reaction was obtained by using the inverted matrix method of Penfold and Leiss. The integrated cross sections from threshold to 10 MeV and to 14 MeV are 2 and 16 MeV ·mb, respectively. These values are in agreement with earlier experiments. The cross-section curve shows peaks at 6.2, 7.5, 8.2, 9.1, 11 and 13 MeV, the last two being in the pygmy resonance energy region. The angular distributions of photoneutrons were measured at different values of E_γmax. The data were analyzed for the distribution of neutrons from each peak. The significant features of the cross-section curve and the angular distributions of neutrons from the peaks are discussed and compared with the theoretical ones reported by several authors. The integrated cross section from the threshold to 10 MeV is much smaller than those calculated on the basis of a pure single-particle model. The neutrons in the pygmy resonance energy region follow a 1+0.46 sin²θ angular distribution, while a 1+1.5 sin²θ distribution is expected from the single-particle picture of the pygmy resonance. These discrepancies are interpreted in terms of the mixing of core excitations and single-particle excitations.
Energy levels of light nuclei A = 13-15
1970, Nuclear Physics, Section A

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Nuclear Instruments and Methods

Abstract

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Cited by (8)

The photoneutron cross section in <sup>13</sup>C

High-energy levels in <sup>13</sup>N (II)

Time-of-flight scattering spectroscopy

A facility for fast neutron time of flight experiments

Photoneutrons from <sup>13</sup>C at photon energies up to 14 MeV

Energy levels of light nuclei A = 13-15

Photoneutron spectrometry by time of flight☆

Abstract

Nucl. Phys.

Nucl. Phys.

J. Phys. Radium

Phys. Rev. Letters

Nucl. Instr. and Meth.

Zeit. Electrochem.

Nucl. Phys.

Doct. Diss. M.I.T.

Doct. Diss. M.I.T.

Progress Reports of the Lab. for Nucl. Sci., Linac Group, Mass. Inst. of Tech.

Phys. Rev.

Physics Letters