High-Resolution in-flight Spectroscopy

High-Resolution in-flight Spectroscopy (HISPEC)

Leader: Prof. M. A. Bentley – University of York

Institutions: Surrey, York, Daresbury

HISPEC is a versatile, high-resolution, high-efficiency spectroscopy set-up to address questions in nuclear structure, astrophysics, and reactions using radioactive beams with energies of up to 200 MeV per nucleon. In-beam gamma−ray and particle spectroscopy after Coulomb excitation and other reactions in the low to intermediate energy regime will be performed using the AGATA Ge array and charged-particle detectors.

The main objective of the HISPEC project is to perform in-beam gamma-ray spectroscopic studies of exotic nuclear species delivered by the Super-FRS. AGATA will be the gamma-ray spectrometer located at the target position. Exotic nuclei will be identified event-by-event by their mass A and charge Z. Another key component of HISPEC is therefore the ion (and particle) identification which will be performed downstream of the target position by LYCCA – the Lund-York-Cologne Calorimeter. LYCCA has two major tasks, namely: (i) to track the reaction products in conjunction with detectors at the secondary-target position; and (ii) to identify A and Z of the secondary reaction products as well as their momenta on an event-by-event basis. The design of LYCCA is based on experience with a system used for the same purpose during the RISING Fast Beam Campaign – the Calorimeter Telescope CATE. LYCCA will have increased count-rate capabilities due to increased granularity and will include target-LYCCA time-of-flight measurements which will be crucial for mass identification. The LYCCA design has ΔE-E modules comprising Si-DSSD (double-sided Si-strip detector) for energy-loss and position measurements and CsI detectors for full-energy measurements, which are preceded by a “timing wall”, most likely consisting of polycrystalline CVD diamond detectors. The first prototype modules have already been assembled, with in-beam tests having taken place in September 2010, and a prototype array (LYCCA-0) will be used for PRESPEC physics experiments in 2010-2011. These experiments will provide guidance for which time-of-flight method to use for the final LYCCA array, which must be ready for the start of the HISPEC programme. Stand-alone LYCCA will be essential for all in-beam experiments until a fully-instrumented magnetic spectrometer is completed and commissioned, after which it will be used in which-ever configuration suits the experiment. The UK is taking the leading role in the development of CVD diamond detectors for the LYCCA time-of-flight system.

The essential devices for HISPEC are therefore a gamma-ray array with position resolution (principally AGATA) and devices for tracking and identifying the recoiling products – these are the LYCCA detector telescope array (Lund-York-Cologne Calorimeter) and the future planned magnetic spectrometer (which would also use LYCCA at the focal plane). In addition to our leading role in AGATA (on separate grant), we are contributing to HISPEC in three areas where there are specific requests for UK leadership: the UK component of LYCCA, mechanical design and electronic engineering. In addition, the UK is leading in several aspects of the AGATA project, relevant to PRESPEC/HISPEC. These include the mechanical design, the production of the front end electronics and detector characterisation.