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Brussel, M.K. Ritchie, Buddy Boyce 2011-05-04T19:48:00Z 2011-05-04T19:48:00Z 10000-01-01 1991 "Bremsstrahlung photons with endpoint energies from 55 to 100 MeV were used to photodisintegrate 6Li nuclei, and emitted neutron/proton pairs were observed in coincidence. Measurement of the energies and angles of the emitted pair allowed reconstruction of the photon energy, as well as the recoil angle and energy of the residual 4He nucleus. Cross sections for the 6Li(l,np) reaction were computed by normalizing the data to measured yields and published cross sections for the 2H( 1 ,np) reaction. The 6Li target was in the form of solid metal foil. Protons were detected with a ~E-E scintillator telescope, and their energy measured by the amount of energy deposited in the ""E"" element (a Nal crystal). The neutron detector was a large solid angle array of long plastic scintillator elements. Neutron trajectories were resolved within the coverage of the array through a combination of detector element identity and the difference in arrival times of scintillation photons at either end of that element. Neutron energy was determined by measuring the time of flight of the neutron over a distance of ~4 m. Cross sections were measured with the proton detector fixed at 81 o (in the laboratory frame) for neutron angles of 50-120°. In addition, measurements were made with detectors at equal angles of 71-101 o on opposite sides of the photon beam. The singly differential cross section ( da / dO.P) at f)P = 81° was calculated by integrating over the neutron angle; its ratio to the deuterium cross section varied from 0.26±0.03 at 45 MeV to 0.55±0.12 at 95 MeV. Cross sections were also evaluated in terms of the recoil momentum of the residual 4He nucleus, which should reflect the combined momentum of the neutron-proton pair prior to the photoabsorption. The distribution of recoil momentum transverse to the photon beam had a central peak of width 96.8±3.5 MeV /c (FWHM); this is consistent with a harmonic oscillator 2s wave function description of the pair-41-Ie relative motion with width parameter qo = 91.5 ± 3.3 MeV jc." Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-05-04T19:48:00Z No. of bitstreams: 1 1991_ritchie.pdf: 6821669 bytes, checksum: d43ed16ae3b5bbd7009ad421f115894f (MD5) Made available in DSpace on 2011-05-04T19:48:00Z (GMT). No. of bitstreams: 1 1991_ritchie.pdf: 6821669 bytes, checksum: d43ed16ae3b5bbd7009ad421f115894f (MD5) Previous issue date: 1991 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Carolyn Mead (cmead2@illinois.edu) on 2011-05-04T19:48:00Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:12:21-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: Thesis Thesis U of I Only 3486385 http://hdl.handle.net/2142/18914 en 1991 Buddy Boyce Ritchie coincident neutron proton pairs lithium photodisintegration Coincident neutron/proton pairs from 6̳Li photodisintegration with 40-100 MeV photons Dissertation / Thesis text Physics Physics University of Illinois at Urbana-Champaign Dissertation Ph.D.