Ultra-High Resolution Silicon Strip Detector Array for Reaction Studies

1. In-ring detector systems PJ Woods University of Edinburgh

2. Main objective To construct an internal silicon strip detector array for ultra high resolution reaction studies using 5-10 MeV/u radioactive ion beams injected into the TSR storage ring. Status: fully funded as part of UK ISOL-SRS project by STFC. T Davinson (Edinburgh) project manager of this workpackage Key scientific objective is to explore properties of resonances dominating reaction rates of radioactive nuclei in astrophysical environments  Consider current state-of-the art of such studies with radioactive beams and inverse kinematics.

3. Galactic abundance distribution of the cosmic γ-ray emitter 26Al INTEGRAL satellite telescope - 2.8(8) Msun of 26Al in our galaxy [R. Diehl, Nature 439 45(2006)]

4. Supernova Cycle

5. Potentially key s-wave astrophysical resonance identified However, resonance strength ωγfor critical low T 26Al hydrogen burning regime in massive stars is unknown

6. use transfer reactions to estimate Гp for (p,γ) reactions where resonance has Гp<< Гγ , ωγis proportional toГp. Гp α Pl (barrier penetration factor) X S(spectroscopic factor) σtransfer = σDWBA X S

7. High resolution d(26gAl,p)27Al study of analog states of 27Si resonances using Edinburgh TUDA Si array @ ISAC II Triumf 150 MeV 26gAl beam bombarding 50 μg.cm-2 (CD2)n target Ibeam~ 5*108 pps target proton 26gAl beam Silicon detectors placed at backward angles, corresponding to forward angle transfer in CoM

8. Energy Resolution in lab frame ~ 40 keV (FWHM)

9. Analogue states to key astrophysical resonances Continuous background due to protons from fusion reactions with Carbon atoms in target

10. Resonance strength depends on strength of low l-component of transfer cross-section which peaks at forward angles

11. In-ring DSSD System for ultra-high resolution (d,p), (p,d) and (3He,d) transfer studies UK ISOL-SRS project For ultra high resolution mode resolution should be entirely limited by transverse beam emittance • Resolutions approaching 10 keV FWHM feasible Pure, thin targets

12. Silicon detectors must be operated in ultra-high vacuum conditions (<10-10 mbar) using UHV materials and must be bake-able to 200°C. Additionally, they must be moved on fast actuators; during injection and cooling phases of the ring operation. UHV materials will be required: sintered ceramic wafer carriers; silver-loaded, low vapour pressure epoxies as solder substitute; Kapton™ cabling. The array shown above consists of MSL-type BB18-1000 double-sided strip detectors (DSSD) These DSSDs have a large surface area of 8x8 cm, with thickness of 1mm, and 128x128 strips. The operational concept is to instrument up to eight DSSDs with a flexible configuration to suit the specific reaction to be studied (upstream or downstream of the reaction site; closer where efficiency is important; further back when kinematic broadening is limiting). The array will use instrumentation from the AIDA system developed for FAIR, and now operating in RIKEN. This consists of ASCI instrumentation of DSSDs, integrated with multiplexed peak-sensing ADC readout, plus 50MSPS 14-bit sampling ADC readout, together with data handling and processing by a Xilinx Virtex 5 FPGA (including PowerPC CPU core running Linux and the UK-standard MIDAS DAQ software package). Readout is via G-bit Ethernet. This liquid-cooled system with 18-layer PCBs will operate outside of the UHV vacuum. It can be used with a wide variety of different geometry detectors, most straightforwardly with strip pitches between 0.25 and 1 mm in multiples of 64 channels.

13. Significant luminosity gains for heavy ions up to A~70

14. Particle detectors Gas jet Pioneering new technique on ESR (Heil, Reifarth) – heavy recoils detected with double-sided silicon strip detector (Edinburgh) Position distribution of recoiling ions measured by DSSD σ(p,γ)= 3.6(5) mb ~10 MeV/u New DSSD system successfully developed (Edinburgh/GSI/Frankfurt) for use in UHV to measure p-process capture reactions in Gamow burning energy region – operated using Xe beam on ESR (2014)

15. New UK ISOL-SRS grant also fully funds system for zero-degree capture of heavy recoil products positioned downstream of first TSR dipole. • p-process measurements will require upgrade of EBIS to produce fully stripped heavy radioactive nuclei (A>70) System can also be placed upstream of dipole for near zero degree coincidence measurements involving particle unbound resonance states.  see pioneering work on ESR at GSI

16. Study of the p(20Ne,2H)19Ne transfer reaction on the ESR heavy ion storage ring @GSI, PJW, Y Litvinov et al. 10820Ne ions @ 50 MeV/u 8 m ESR Electron cooler 1013 H2/cm2 gas target

17. Detector Pocket Si –telescope • 2 x ~1mm ‘W’-type detectors • 16x16 strips

18. Particle ID plot for DSSD d ΔE1 fast α’s p E1 + E2

19. A few hours of data from test run on ESR DT Doherty, PhD Thesis (2014) Resolution ~200 keV FWHM limited by beam spot size/angular resolution

20. Forward moving heavy ions in coincidence with tritons

22. Status Summary The internal detector systems for the TSR@ISOLDE project have been fully funded. The first overall ISOL-SRS project meeting has taken place at Daresbury, including external spectrometer system using extracted beams – see next talk of Robert Page). Important next stage of detailed design and development of systems, including wider liaison within collaboration, for incorporation of system into the ring.  in parallel, funding is being sought for internal target development by J Cederkaal (Lund) and H Fynbo (Aarhus)