P. Thieberger

The total neutral energy spectra in the central region of α−α, d−d and p−p interactions at sNN = 31 GeV per nucleon pair at the CERN ISR

The spectra in total neutral energy, ETOT0, have been measured in pp, dd and αα collisions at centre-of-mass energy per nucleon pair, sNN, of 31 GeV. The range in ETOT0 covered was 1 to 19 GeV in pp, 18 to 24 GeV in dd and 1 to 34 GeV in αα interactions. The ratio of the αα to the pp spectra rises monotonically from 7 at ETOT0 = 1.5 GeV to 105 at ETOT 0 = 19 GeV. Since ETOT0 is the sum over many particles in the detector, it is directly sensitive to multiple nucleon-nucleon collisions in the interacting α particles. The αα spectrum in the range 8 < ETOT0 < 17 GeV is consistent with being described by a simple model of 4 simultaneous nucleon-nucleon collisions with a cross section about equal to 10% of the observed αα interaction cross section. The spectrum of ETOT0 above 17 GeV is even flatter than this extreme case where four nucleon pairs are interacting.

Band structure of 184Ir

Abstract States of 184Ir, excited through several (HI, xn) reactions were studied using in-beam γ-ray and conversion electron spectroscopy techniques. A new high-spin level scheme, comprising three different rotational bands is presented. The negative-parity ΔI = 1 ground-state band is the most complete example of the semidecoupled \ gp h 9 2 ⊗ v i 13 2 structure, in a prolate deformed situation, known to date. The other two bands are the doubly decoupled \ gph 9 2 ⊗ v 1 2 − [521] and a ΔI = 1, \ gp 5 2 + [402]⊗v i 13 2 based structure of the compressed type.

Multiple band structure in 156Er

Abstract The 142Nd(18O, 4n)156Er reaction at 90–95 MeV was used to study 156Er high-spin states to spin 24. In addition to the background ground-state band, two well developed odd-spin side bands, one of each parity, were observed.

Lifetimes and g-factors of the 6− and 7− isomers in 66Ga and 68Ga

Abstract The 6 − and 7 − isomeric states in 66 Ga and 68 Ga at 1440.9 and 1229.6 keV, respectively, have been populated with the ( 13 C, 2np) and ( 15 N, n2p) reactions on natural Fe. The half-lives of these states have been measured to be T 1 2 (6 − , 66 Ga ) = 57.3 ± 1.2 ns and T 1 2 (7 − , 68 Ga ) = 64 ± 2 ns . Using previous data on the hyperfine field of Ga in Fe, the g -factors of these states have been determined by means of the TDPAD method. The results are g(6 − , 66 Ga ) = 0.129 ± 0.003 and g(7 − , 68 Ga ) = 0.105 ± 0.003 . These values are in very good agreement with the independent particle model if one assumes the {π f 5 2 , ν g 9 2 } 6 − ,7 − and {π p 3 2 , ν g 9 2 } 6 − configurations and uses the empirical proton and neutron g -factors from odd- A neighboring nuclei instead of the Schmidt values. The large disagreements with experiment when Schmidt values are used show that core polarization effects are important in these nuclei.

Test of heavy-ion gas-foil stripping for improved foil lifetime in Tandem Van de Graaff accelerators

Abstract A heavy-ion stripping arrangement consisting of gas stripping in the high-voltage terminal and foil stripping at the 3 4 V t point has been successfully tested at the Brookhaven Tandem Van de Graaff facility. When injecting a NiO− beam, the foil lifetime at the second stripper was about 30 times longer that observed when a foil stripper at the high-voltage terminal received the same beam current. This effect is attributed to larger beam energy and lower beam density at the second stripper location. Charge-state distributions obtained with this arrangement are shown in terms of an intensity-versus-energy diagram and compared to similar curves for single-foil, dual-foil and single gas stripper.

The Brookhaven National Laboratory three-stage MP Tandem Van de Graaff facility

Abstract The Brookhaven National Laboratory three-stage MP Tandem facility has been in operation for over four years since its construction completion. A number of modifications and improvements have been made in the accelerator system to extend its capabilities beyond the original design. These improvements and the current performance capabilities for two- and three-stage operation will be discussed.

A new pulse height compensator for time to amplitude converters

Abstract The pulse height dependence of the time measurement performed by a time to amplitude converter is canceled by using correcting signals from a second converter to which slow pulses from the detectors are fed. A maximum displacement of the prompt curve of 3 × 10 −11 sec is obtained over a pulse height range of ratio 1 to 5.5 for both detectors.

High-spin bands in117,119I and118Xe

Excited states in117I,118Xe and119I were populated in the reactions106Pd+16O and108, 110Cd+12C. The groundstate band in118Xe was observed to its (18+) member and the 11/2− bands in117I and119I to their (35/2−) and (43/2−) members, respectively. The structure of the bands in the I isotopes is interpreted as aπ h11/2 proton coupled to an even-even band structure in Xe, and the band crossings observed in118Xe and119I are interpreted in the Cranked Shell Model framework asABn ofv h11/2.

The north american MP tandem accelerators

Abstract The main features of the six North American MP tandem Van de Graaff accelerators are summarized as well as some of their main performance characteristics. The latest accelerator-related studies, developments and improvements are described for each facility. Ongoing and proposed future developments at some of these laboratories are briefly discussed.

Long-lived positive parity isomer in 76Br

Abstract A 4+, 1.3 s isomer has been found at 102.6 keV in 76Br using the 75As(α, 3n) reaction. A previously reported band structure is interpreted to decay into this isomer of probable π g 9 2 ⊗ ν g 9 2 parentage.