DESPEC Report: NuSTAR Management Meeting12th July 2010

• DeSPEC Project formally started April 2010.• Full array of (~)36 LaBr3 detectors and mechanical holders to be used with

AIDA in PreSPEC decay campaign (2013).• Personnel Issues:

– DESPEC PDRA (Brighton) advertised, deadline for applications 13th July; PDRA to start Oct. 2010.

– DESPEC PhD student (UWS) to start Oct. 2010• In-beam tests of different types of LaBr3 detectors for evaluation ‘in-beam’

and with sources. 3 types of LaBr3 detectors 2”x2”, 1.5”x1.5” and other ‘conical’ style detectors.– Experiment to test these in-beam in Bucharest June 2010.

• Analysis of in-beam data and MC simulations to be performed by PDRA Oct 2010 – Dec. 2011– (source) tests with AIDA Oct 2010 – July 2011– (Pre-SPEC Decay) meeting to discuss pan-European integration of LaBr3

fast-timing detectors, to take place in Brighton 9-11 Jan 2011.

To do (soon)

• LaBr3 source tests with AIDA (Oct. 2010 – July 2011)

• Design of test holding structure for test detectors (Dec 2010 – April 2011)

• EDAQ design (June 2011 – March 2012)

Precision Measurement of the Lifetime of the I=4- Intruder State in 34P Using

Ge-LaBr3-LaBr3 Fast-Timing Coincidences

Experiment at the Bucharest Tandem 23rd June – 2nd July 2010

Surrey Uni., Brighton Uni. (UK) UGC-DAE KolkataIFIN-HH Bucharest

Uni. Notre Dame, Florida State Uni. (USA)Istanbul University (Turkey)

Sofia (Bulgaria)KACST (Saudi Arabia)

Physics Motivation

4- 2305

• Recent study of neutron-rich, N=19 nucleus34P identified low-lying I=4- state at Ex=2305 keV.

• Spin and parity assigned on basis of -ray DCO and polarization measurements.

• I=4-→ 2+ transition can proceed by M2 and/or E3.

• Aim of experiment is to measure precision lifetime for 2305 keV state → obtain B(M2) and B(E3) values.

• Previous studies limit half-life to 0.3 ns < t1/2 < 2.5ns

Lifetime gives a direct comparison with sdfp-shell model calculations, i.e., including (intruder) negativeparity (neutron) f7/2 and p3/2 orbitals.

Experiment

• 18O Beam (from Li18O2 mixture)• 50 mg/cm2 Ta2

18O5 enriched target• 36 MeV 18O beam from Bucharest Tandem

(typical beam current ~20 pnA)• 34P from pn evaporation channel (~5-10mb)• Measure reaction gammas from array of

8 x HPGe and 7 x LaBr3 detectors.• Master gate, either (LaBr3)2 OR (HPGe)3 for a

valid event.

• Populate near-yrast states in 34P via 18O(18O,pn)34P reaction.

Total projection from 18O+18O reaction 34 MeV (from Chakrabarti et al.,)

*

• Measure reaction rays using Bucharest array of 8 x co-axial HpGe (for 34P channel selection) plus 7 x LaBr3 scintilation detectors (for fast-timing).

• Gate on Ge measurement of 429 keV or 1876 keV transition to select 34P ions. Selects these ions from other evap channels. 31S (n); 33P(p2n), 33S (2pn), 34S (2p).

2” x 2” detectors; 1.5”x1.5” detectors and 2 x ‘conical’ LaBr3 detectors…in-beam and source data taken (152Eu, 60Co, 56Co)… analysis on going.

LaBr3 energy spectrum in coincidencewith the 1876 keV peak (34P: 4- →2+) in the germanium detectors.

Lifetime of the I=4-, Ex=2305 keV state in 34P.

Time (TAC) difference spectrum between the 429 keV (2+ →1+) & 1048 keV (5- →4-) transitions in 34P, AND gated by the 1876 keV (4- →2+) in any of the HPGe detectors.

50 ps/ chan.

T1/2~1.5(1) ns

Time difference spectra between 1968 and 968 keV transitionsin 33S gated by energies measured in the LaBr3. ‘Fast’ transition shows prompt response function by comparison.

T.Alharbi, N. Marginean, P.H. Regan et al., Surrey, Bucharest, Brighton, Notre Dame, Florida State, Sofia, Istanbul, Koolkata, KACST collaboration.

IFIN-HH Bucharest (Romania), Surrey Uni., Brighton Uni. (UK), UGC-DAE Kolkata (India)Uni. Notre Dame, Florida State Uni. (USA), Istanbul University (Turkey), Sofia (Bulgaria), KACST (Saudi Arabia) collaboration.