CR Time-of-Flight detector Present status Marcel Diwisch II. Physikalisches Institut, Justus-Liebig-Universität Gießen, Germany Outline Isochronous Mass Spectrometry Dual ToF detector system at CR New dimensions of ToF detector Technical issues

Overview FAIR ESR

Isochronous Mass Spectrometry (IMS) at FRS-ESR Time-of-Flight detector Resolving power: FWHM = 2 x 105 Accuracy: 10-6 Half-life: ~10 s B ~ 10 mT E ~ 1 kV/cm Developed in Gießen (J. Trötscher NIM B70:455–458, 1992)

Overview FAIR CR

Velocity measurement = improve isochronicity Collector Ring Injection (*) S. Litvinov, PhD thesis (2008) L = 221,45 m Bρ = 13 Tm γt = 1,43-1,84 Δp/p = (0,22 – 0,62)% εx = 100 mm mrad (*) isochronous mode magnet stoch. cooling pick-up/kicker inj./extr. kicker RF cavity detectors / beam diagnostics valves TOF-1 Figure: A. Dolinskii Dual detector system: Velocity measurement = improve isochronicity TOF-2

CR Simulations Monte Carlo simulations (MOCADI) for 10000 ions circulating in the CR with γt=1,67 Present 40 mm diameter of foil is too small for needed acceptance ⇒ 80 mm diameter of foil

Design of new detector Main challenge: Possible solution: larger carbon foil diameter needed increase carbon foil diameter to 80 mm   larger total detector geometry higher electrical field strength longer flight path from foil to MCPs better homogeneity of (electrical) fields larger absolute time of flight by changing electrode shape time uncertainty increases and electrode positions limited space in CR

CR Simulations SIMION grid creation and calculation of electrical fields CAD-drawing y x z ESR-ToF Detector CR-ToF Detector x-dimension 300 mm 565 mm y-direction 90 mm 180 mm z(beam)-direction 154 mm 236 mm Simulation of secondary electrons

Design of new detector (Electrodes) Efficiency forward (%) 77,4 Efficiency backward (%) 76,8 Efficiency coincidences (%) 66,9 Timing accuracy (ps) 37 Efficiency forward (%) 97,0 Efficiency backward (%) 97,2 Efficiency coincidences (%) 96,6 Timing accuracy (ps) 25 Electron Transport Only

Design of new detector (Magnet) COMSOL simulations for necessary magnet homogeneity needed relative homogeneity: <10-3 in a 180 mm radius with 240 mm gap 198 mm poleshoe diameter minimum 800 mm

CR Simulations ESR CR L = 108 m L = 221,45 m Bρ = 6,4 Tm Bρ = 13 Tm Δp/p = 0,2 % εx = 7 mm mrad L = 221,45 m Bρ = 13 Tm γt = 1,67 Δp/p = 0,5 % εx = 100 mm mrad TOF detector (1x) TOF detector (2x) B-field homogeneity radius 100 mm B-field homogeneity radius 200 mm Foil diameter 40 mm Efficiency ≈ 78% Timing accuracy ≈ 45 ps Foil diameter 80 mm Efficiency ≈ 98% Timing accuracy ≈ 35 ps

Technical Issues Construction of TOF detectors in ESR same technique will be used for CR But magnets and detector will be larger!!!

Technical Issues

Tests for new detector Questions: 80 mm foils produceable? Yes! TU Munich produces them Can one handle 80 mm foils? Will be tested Impact of larger foils to timing? Will be tested First measurements with 40 mm foils have been performed

Acknowledgements ILIMA TOF Detector Working Group U. Czok, T. Dickel, M. Diwisch, H. Geissel, C. Hornung, R. Knöbel, N. Kuzminchuk-Feuerstein, W.R. Plaß, C. Scheidenberger, H. Weick Dr. T. Faestermann and Dr. R. Gernhäuser for providing us with carbon foils Funding: BMBF (06GI9115I), HGF (NAVI), GSI (strategic university cooperation GSI-JLU-FAIR) HIC for FAIR

Velocity determination Second term of equation not vanishing for non isochronous ions Correction by measuring velocity in 22 m distance: