CJ Barton Department of Physics INTAG Meeting – GSI – May 2007 Large Acceptance Bragg Detector at ISOLDE

CJ Barton Department of Physics Introduction Background Detector Ideas Simulations and Design ISOLDE large beam species availability and increased beam energies will continue to open exciting research opportunities in nuclear physics

CJ Barton Department of Physics Sample Reaction – Multiple Coulomb Excitation 1.3 MeV Efficiency: 19% Resolution: 7 keV at v/c Angular Range  = 2 0  = MiniballCompact Disc Array Particle Energy Detection and Position Resolution Not always sufficient (Kinematics & Isobaric contamination)

CJ Barton Department of Physics Ion Chamber Idea Segmented Ion Chamber Z identification (Target/Beam/Isobaric Contamination) 0 0 hole for beam suppression/count rate and flux integration  /2 for detection of target and scattered beam Large acceptance for efficiency Position-sensitive (angular distribution measurement and some Doppler correction) Allows for particle array(for stable target nuclei) near 90 0 Allows for high-efficiency  -ray array around target

CJ Barton Department of Physics Idea – Annular PPAC+Ion Chamber Segmented Anode Front View Segmented Anode Side View PPAC 2 o resolution 1mm Frish Grid X X Radial Field Challenge – segmentation for good  E/E Conclusion – do not pursue  E (MeV) E (MeV) Te 40deg Te 10deg I 10deg I 40deg  E/E Plot Z ~ 50

CJ Barton Department of Physics Other Ideas: Gas-Silicon Hybrid Gas EE Gas-Silicon Hybrid Position Sensitive Si Challenge – 1/20 Z resolution (parallel capacitance) Most effective with  E having about 50% E loss Challenge – Z resolution Conclusion – do not pursue Front View Side View

CJ Barton Department of Physics Other Ideas: PPAC and Bragg Range in Bragg (50 mbar isobutane) /- 0.2 cm Radial Extent Angle Straggling / cm / degrees As Se Cl Side View PPAC 2 o resolution 1mm X Frish Grid X Front View

CJ Barton Department of Physics Bragg Design Inner Tube field shaping rings Field Gradient! Electron Trajectories Anode Segmentation and non-normal trajectories

CJ Barton Department of Physics Bragg Design – normal MINIBALL configuration Vacuum Hole 10 degrees front 3 degrees back Challenges: Background

CJ Barton Department of Physics Bragg Design – altered MINIBALL configuration Bragg Challenges: MINIBALL position Anode Segmentation Drift of Charge And Anode Segmentation E Field Z – resolution ~ 1/20 !

CJ Barton Department of Physics Bragg Design – Normal orientation Too Simple – Too Hard to Construct 15 o 55 o 35 o Side View (Slice) Target Chamber Flared With Radial Field

CJ Barton Department of Physics Thick Target Simulation: 70 Se Beam Spot (5mm diameter) + Straggling Front Beam Axis Back 30 o 202 MeV 70 Se, 70 As 25 cm Beam Spot Angle: /- 0.4 deg Thick Target Energy 169 MeV (front) 146 MeV (middle) 128 MeV (end) 2 mg/cm Pd 2.88 MeV/  1x10 4 / sec Range Straggle +/ cm Radial Straggle +/- 0.8 cm Angle Straggling 2.4 +/- 0.2 degrees

CJ Barton Department of Physics Thick Target Simulation: 70 Se Rutherford Calculation (projectile and scattered target) overlap CoulEx Calculation

CJ Barton Department of Physics 132 Te CoulEx Experiment with Bragg Beam Axis 1 mg/cm 2 48 Ti 132 Te, 132 Sb 1x10 6 / sec 3.1 MeV/  Range in Bragg /- 1.0 cm Radial Extent Angle Straggling 0.8 +/- 0.6 cm 1.2 +/- 0.9 degrees Te Ti Sb

CJ Barton Department of Physics Calculations: 132 Te Rutherford Calculation (projectile and scattered target) CoulEx Calculation overlap

CJ Barton Department of Physics Limitations Electron Drift Radial Straggle ~ 1mm Electron Drift Time to Peak ~ 1  sec (Field Gradient) Rutherford Scattering – Physical Barrier (per experiment) for space charge Anode Pad Segmentation Efficiency and Isolation

CJ Barton Department of Physics Current Design (geant4) cm cm 25 cm 2.0 cm 10 0 Segmented Anode Plates Beam Line Guide Element 1 10 o -30 o Note Gap Element 2 30 o -50 o

CJ Barton Department of Physics Current Design (geant4) Note Gap

CJ Barton Department of Physics Solid Angle of Detector

CJ Barton Department of Physics Map of 1 Segment - Garfield Electric Field Gradient ~ 100 V/cm Cathode-Grid ~ 28 cm Grid-Anode ~ 2 cm Segmented Anode Frisch Grid Grounded Outer Surface Labels

CJ Barton Department of Physics Voltage Contour Map of 1 Segment Note gap

CJ Barton Department of Physics Ion Track and Ionization Segmented Anode

CJ Barton Department of Physics Ionization Profile and Signal SRIM Ionization profile Garfield Charge Density Garfield – induced signal Current versus Time Z

CJ Barton Department of Physics Signal Distribution on Pad Whole Signal Arrival TimeElectron Offset ~ 1mm

CJ Barton Department of Physics Technical Drawing Larger at 53 o and 6 o Modified Ring supports

CJ Barton Department of Physics Technical Drawing

CJ Barton Department of Physics Technical Drawing 6 Identical Segments 2 Elements in each Segment

CJ Barton Department of Physics Technical Drawing 4 segmented Anode Pads Per Element 48 Anode Channels

CJ Barton Department of Physics Technical Drawing

CJ Barton Department of Physics Technical Drawing

CJ Barton Department of Physics Plans Finish Design of Bragg Volume (gas flow + support) PPAC Design + target chamber + transit line Construct and Test 1 segment (2 elements) Improve Garfield simulation of detector Incorporate into Miniball Geant4 simulation (efficiency)

CJ Barton Department of Physics People University of York CJ Barton, JE Butterworth, D Bandyapadhyay, P Joshi, P Mumby-Croft, PE Kent Manchester University JF Smith, BJ Varley STFC Daresbury M Labiche, R Griffiths, J Strachan CERN/ALICE R Veenhof