E.W. Macdonald

Development of a silicon strip detector array for nuclear structure physics

Abstract The Edinburgh nuclear physics group has been exploiting some of the unique features of silicon strip detectors (SSDs) in a variety of nuclear structure experiments using high energy photons and heavy-ion projectiles. Current experimental applications make use of large area (≈ 4−25 cm 2 ), totally depleted SSDs with depletion thicknesses in the range ≈ 150−1000 μm and strip pitches of 2000 μm. In addition, two new device configurations are currently undergoing evaluation tests for future applications. These configurations are: (i) double-sided silicon strip detectors (i.e. “quasi-pixel” devices) and, (ii) position sensitive silicon strip detectors. Silicon strip detectors are potentially a powerful tool for nuclear structure physics applications where charged particle detection is required. It is possible to construct charged particle detection systems with good energy and position resolution, large solid angle and high data throughput. To date however, it has not been possible to fully exploit the potential of SSDs because of the high cost and limited availability of appropriate instrumentation. To overcome this problem we are developing low cost hybrid microelectronic instrumentation in collaboration with the SERC Rutherford-Appleton Laboratory.

Tensor analyzing powers for Li induced transfer breakup reactions

The tensor analysing power T/sub 20/ has been measured for the /sup 120/Sn(/sup 7/Li, /sup 8/Be to 2 alpha )/sup 119/In and /sup 120/Sn(/sup 7/Li, /sup 6/Li* to alpha +d)/sup 121/Sn transfer breakup reactions at 70 MeV bombarding energy. Coupled channels and continuum discretized coupled channels calculations, incorporating a detector phase space correction, were found to give good agreement with the data.

A high efficiency 8Be detector

Abstract A very high efficiency 8Be detection system, based on silicon strip-detectors, has been developed. The theoretical performance of the system is evaluated by the use of Monte Carlo simulation methods and the experimental performance is investigated by a study of the reactions 12C, 120Sn(9Be, 8Be).

A new technique for spin alignment measurement and application to the study of resonances in 12C on 12C collisions

Abstract A new technique has been developed for measuring spin alignment in heavy ion collisions which excite nuclear states above breakup threshold. Breakup fragments are detected in position sensitive silicon strip detectors, in coincidence with the recoil from the collision. The alignment can be determined from the spatial distribution of the fragments. This technique has been applied to the study of resonances in 12 C on 12 C collisions. The 9.64 MeV 3 − state in 12 C is excited, which breaks up into 8 Be + α and t the 8 Be breaks up into two α-particles.

Kinematically complete study of the Li7(p, )8Be*2± reaction at Ep=25 MeV

A kinematically complete study of the {sup 7}Li({ital p},{gamma}){sup 8}Be{sup *}{r arrow}2{alpha} reaction at {ital E}{sub {ital p}}=25 MeV is described. An upper limit of {ital d}{sigma}/{ital d}{Omega}{lt}0.04 {mu}b sr{sup {minus}1} is reported for the {theta}{sub {gamma}}=90{degree} capture cross section to the 2{sup +} states at 16.62 and 16.93 MeV, which is five times smaller than published results. This new datum is shown to be more consistent with a semidirect reaction mechanism involving the giant dipole resonance built on the {sup 8}Be{sup *} 2.94-MeV state than the previously proposed direct reaction mechanism.

Tensor Analysing Powers for 7Li Induced Transfer Breakup Reactions

The tensor analysing power T20 has been measured for the 120Sn(7Li,8Be → 2α)119In and 120Sn(7Li,6Li* → α + d)121Sn transfer breakup reactions at 70 MeV bombarding energy. Coupled channels and continuum discretized coupled channels calculations, incorporating a detector phase space correction, were found to give good agreement with the data.

Kinematically complete study of the sup 7 Li( p ,. gamma. ) sup 8 Be sup * r arrow 2. alpha. reaction at E sub p =25 MeV

A kinematically complete study of the {sup 7}Li({ital p},{gamma}){sup 8}Be{sup *}{r arrow}2{alpha} reaction at {ital E}{sub {ital p}}=25 MeV is described. An upper limit of {ital d}{sigma}/{ital d}{Omega}{lt}0.04 {mu}b sr{sup {minus}1} is reported for the {theta}{sub {gamma}}=90{degree} capture cross section to the 2{sup +} states at 16.62 and 16.93 MeV, which is five times smaller than published results. This new datum is shown to be more consistent with a semidirect reaction mechanism involving the giant dipole resonance built on the {sup 8}Be{sup *} 2.94-MeV state than the previously proposed direct reaction mechanism.

Kinematically complete study of theLi7(p,γ)8Be*→2α reaction atEp=25 MeV

A kinematically complete study of the {sup 7}Li({ital p},{gamma}){sup 8}Be{sup *}{r arrow}2{alpha} reaction at {ital E}{sub {ital p}}=25 MeV is described. An upper limit of {ital d}{sigma}/{ital d}{Omega}{lt}0.04 {mu}b sr{sup {minus}1} is reported for the {theta}{sub {gamma}}=90{degree} capture cross section to the 2{sup +} states at 16.62 and 16.93 MeV, which is five times smaller than published results. This new datum is shown to be more consistent with a semidirect reaction mechanism involving the giant dipole resonance built on the {sup 8}Be{sup *} 2.94-MeV state than the previously proposed direct reaction mechanism.

The Li+n clustering of Li from the H(Li, d)Li reaction

The T20 analysing power has been measured at 0 degrees for the 1H(7Li,d)6Li reaction leading to the ground and first excited states in 6Li. The data have been analysed in terms of a simple cluster model of 7Li. The T20 value for the ground-state transition is well described assuming a 6Li+n cluster structure for 7Li where the 6Li core acts as a spectator and no nucleon spin flip takes place.

The6Li+n clustering of7Li from the1H(7Li, d)6Li reaction

The T20 analysing power has been measured at 0 degrees for the 1H(7Li,d)6Li reaction leading to the ground and first excited states in 6Li. The data have been analysed in terms of a simple cluster model of 7Li. The T20 value for the ground-state transition is well described assuming a 6Li+n cluster structure for 7Li where the 6Li core acts as a spectator and no nucleon spin flip takes place.