The Elastic Scattering of Co ⁶⁰ γ-Rays

Journal Article · Tue May 01 04:00:00 EDT 1962 · Canadian Journal of Physics

DOI:https://doi.org/10.1139/p62-063· OSTI ID:4839894

Standing, K. G.; Jovanovich, J. V.

Cross sections were measured for 90 deg elastic scattering of Co⁶⁰ gamma rays (l.33 and 1.17 Mev) from aluminum, copper, and tin. They agree with theoretical predictions for Rayleigh and nuclear Thomson scattering. A continuum between the Compton and the elastically scattered gamma rays interfered with the measurements for heavier elements, since it increased rapidly with Z. The continuum was investigated by observing the gamma rays scattered through 60 deg by thin gold foils. It was found to be produced directly by the gamma rays themselves, not by the electrons they knock out of the target atoms. The experimental cross section was compared with that expected for incoherent scattering from the bound atomic electrons. It agrees within a factor of 2 with the cross section given by the form factor approximation, although it is more than an order of magnitude larger than a modification of the form factor, which is based on comparison with elastic scattering calculations. The spectrum of elastically scattered gamma rays from lead was examined by a special method in order to reduce the contribution of the inelastic continuum; two photomultipliers faced a single scintillator and pulses from one photomultiplier were counted only when they corresponded to the largest pulses from the other. The cross section between 12 and l50 deg was found to be much lower than that of most previous measurements. It agrees with the calculated cross section for Rayleigh and nuclear Thomson scattering within the possible errors in the calculations. Therefore the measuiements yield no evidence for the presence of Delbruck scattering, the upper limit on its intensity now being set primarily by the uncertainties in the theory.

• Research Organization: Univ. of Manitoba, Winnipeg
• Sponsoring Organization: USDOE
• NSA Number: NSA-16-019763
• OSTI ID: 4839894
• Journal Information: Canadian Journal of Physics, Journal Name: Canadian Journal of Physics Journal Issue: 5 Vol. 40; ISSN 0008-4204
• Publisher: Canadian Science Publishing
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ALUMINUM
COBALT 60
COMPTON EFFECT
COPPER
CROSS SECTIONS
DELBRUECK SCATTERING
FOILS
GAMMA RADIATION
GOLD
LEAD
MEASURED VALUES
PAIR PRODUCTION
PHOSPHORS
PHOTOMULTIPLIERS
PHYSICS
PULSES
RAYLEIGH SCATTERING
SCATTERING
SCINTILLATORS
SPECTRA
THOMSON SCATTERING
TIN