1. June 2006 Paul Mumby-Croft University of Yor k 1Page TACTIC: A New Detector for Nuclear Astrophysics An update for the ACTAR meeting, Daresbury, UK 12-13 th June 2006. Paul Mumby-Croft Nuclear Physics Group, University of York, UK

2. June 2006 Paul Mumby-Croft University of Yor k 2Page TRIUMF Annular Chamber for the Tracking and Identification of Charged Particles Original concept: L. Buchmann, TRIUMF

3. June 2006 Paul Mumby-Croft University of Yor k 3Page How is it going to work? ● 90% helium 10% CO2 gas mixture ● Pressure of a few hundred mbar ● Drift voltage ~100V/cm

4. June 2006 Paul Mumby-Croft University of Yor k 4Page Technical drawings (Daresbury, P. Amaudruz )

5. June 2006 Paul Mumby-Croft University of Yor k 5Page Technical drawings (Daresbury, P. Amaudruz )

6. June 2006 Paul Mumby-Croft University of Yor k 6Page Technical drawings + GEANT4 (G. Ruprecht, TRIUMF)

7. June 2006 Paul Mumby-Croft University of Yor k 7Page Technical drawings + GEANT4 (G. Ruprecht, TRIUMF)

8. June 2006 Paul Mumby-Croft University of Yor k 8Page The cathode cage ● Purpose: to reduce background ionisation electrons

9. June 2006 Paul Mumby-Croft University of Yor k 9Page The End. Thanks to the TACTIC collaboration: A. Laird 1, G. Ruprecht 2, D. Gigliotti 2, P. Amaudruz 2, L. Buchmann 2, S. Fox 1, B. Fulton 1, T. Kirchner 2,R. Openshaw 2, M. Pavan 2, J. Pearson 2, G. Sheffer 2, P. Walden 2. Thanks to R. Veenhof 3 for help with GARFIELD Thanks to Rob, Kal, and Roy at Daresbury 1) Department of Physics, University of York, York, YO10 5DD, UK. 2) TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3, Canada 3) CERN, CH-1211 Genève 23, Switzerland

10. June 2006 Paul Mumby-Croft University of Yor k 10Page Technical drawings (Daresbury, P. Amaudruz )

11. June 2006 Paul Mumby-Croft University of Yor k 11Page Motivation ● To investigate astrophysical charged-particle reactions ● Low energies and low flux RIBs ● Need good solid angle coverage (c.f. the LEDA array) ● Initial design caters for 8 Li(a, n) 11 B reaction ● Recent r-process models are sensitive to this reaction rate (Sasaqui et al. ApJ 634 2005) ● Transitions to excited states make important contribution ● Factor of ~2 difference in published reaction rates (Boyd et al. 1992; Gu et al. 1995; Mizoi et al. 2000; Paradellis et al. 1990).

12. June 2006 Paul Mumby-Croft University of Yor k 12Page The Gas Electron Multiplier ● Thin Kapton foil (50um) with 10um copper on each side ● Etched with 50um diameter holes (Pictures from CERN)

13. June 2006 Paul Mumby-Croft University of Yor k 13Page The cathode cage

14. June 2006 Paul Mumby-Croft University of Yor k 14Page E-potential around the cathode cage ● Electrons want to drift ‘uphill’

15. June 2006 Paul Mumby-Croft University of Yor k 15Page Summary ● New detector for charged particle reactions ● Active target configuration using GEMs ● Measures timing and total energy, allowing vertex reconstruction ● Technical drawings very near completion, construction begins at York this summer.

16. June 2006 Paul Mumby-Croft University of Yor k 16Page

17. June 2006 Paul Mumby-Croft University of Yor k 17Page

18. June 2006 Paul Mumby-Croft University of Yor k 18Page What do we see?

19. June 2006 Paul Mumby-Croft University of Yor k 19Page Ionisation in TACTIC

20. June 2006 Paul Mumby-Croft University of Yor k 20Page Variation of Gain with Voltage and Pressure.

21. June 2006 Paul Mumby-Croft University of Yor k 21Page What has been done so far? (G. Ruprecht, TRIUMF)

22. June 2006 Paul Mumby-Croft University of Yor k 22Page

23. June 2006 Paul Mumby-Croft University of Yor k 23Page

24. June 2006 Paul Mumby-Croft University of Yor k 24Page

25. June 2006 Paul Mumby-Croft University of Yor k 25Page

26. June 2006 Paul Mumby-Croft University of Yor k 26Page Resolution

27. June 2006 Paul Mumby-Croft University of Yor k 27Page

28. June 2006 Paul Mumby-Croft University of Yor k 28Page E-potential around the cathode cage

29. June 2006 Paul Mumby-Croft University of Yor k 29Page Electric field strength around the wires.

30. June 2006 Paul Mumby-Croft University of Yor k 30Page Drift time: is it uniform in phi? Drift velocity and drift time are fairly insensitive to E (V/cm) at these energies.

31. June 2006 Paul Mumby-Croft University of Yor k 31Page Overview of presentation ● What is a TACTIC? ● Why do we need it? ● How is it going to work?