New gas detectors for the PRISMA spectrometer focal plane

Transcription

1 M. Labiche - STFC Daresbury Laboratory New gas detectors for the PRISMA spectrometer focal plane New PPAC (Legnaro Padova Bucharest Zagreb) & Large Secondary e - Detector (Se - D) (Manchester-Daresbury-Paisley- Legnaro) JRA6: INstrumentation for TAGging (INTAG - task4)

2 The large acceptance tracking Magnetic Spectrometer Q-D: PRISMA Ω = 80 msr ΔZ/Z 1/60 (Measured) ΔA/A 1/190 (Measured) TOF Energy acceptance ±20% Bρ = 1.2 T.m beam MCP Start Detector X,Y & T I MWPPAC Detector 10 sect. X,Y & T F Ionisation Chamber 10x4 sect. ΔE - E

3 Results from PRISMA Z discrimination 40 Ar+ 208 Pb 450 MeV ΔE/E < 2% ΔZ/Z ~ 1/60 for Z=20 Z=30 70 Zn+ 238 U 450 MeV Z=18 Z=17 96 Zr+ 124 Sn 575 MeV Z=40 PIAVE+ALPI Z= Xe+ 208 Pb 950 MeV 3 Energy [arb. units] Courtesy of E. Fioretto - LNL

4 Results from PRISMA Mass resolution A=36 40 Ar+ 208 Pb Z=16 Yield of S isotopes Counts FWHM/centroid 1/160 from P. Mason Mass=92 96 Zr+ 124 Sn Z=38 Mass [amu] Yield of Sr isotopes Counts FWHM/centroid 1/200 Mass [amu] 4 Courtesy of E. Fioretto - LNL

5 New Focal Plane Detectors : Why? Atomic number Efficiency and mass resolution 40 Ar 96 Zr Efficiency Mass separation (1/A) Mass resolution (ΔA/A) Attenuation of the anodic signals produced by the delay lines New PPACs Se - D Large energy straggling for slow moving heavy ions due to the detector windows 5

6 New PPACs for light ions since July cm 15 cm 10 μm diameter Au plated Tungsten wires 1.5 μm Mylar cathode +2x20 μg/cm 2 Al μm 20 μm α ~ 2.8 SE FF (A ~ 120 amu; E ~ 90 MeV) ~ 200 SE

7 Results with α source 241 Am since July 2007 Cathode 10 ns HV tests Filling gas : C 4 H 10 Working pressure : 4-12 hpa Max HV (all configurations) ~ V Tests with α particles from a 241 Am source Rise-time Charge calibration Gas gain (>10 3 ) Pulse height Cathode: V Anodes: V No signal at all with previous PPAC Cathode 50 mv/div X anode 20 mv/div 7

8 In-beam commissioning : How? Time resolution Position resolution Efficiency vacuum vessel START detector MCP 6x4 cm 2 θ = 90 Δθ = msr Beam MCP MCP 197 Au Monitors New PPAC 100x15 cm cm Beam time: 18 th -19 th Dec 2007 Beams: 32 S at 150, 120, 100 and 90 MeV 16 O at 70 and 60 MeV Target: 100 μg/cm 2 Au 8

9 In-beam commissioning : Results since Dec S MeV cathode 200 mv/div 32 S MeV X anode 50 mv/div max (Cathode/Anode) ~ 3 X Position spectrum Peak-to-valley ratio ~

10 In-beam commissioning : Results S MeV Overall time resolution ~ 2 ns Counts including the energy straggling in the Au target, the kinematical broadening and the time resolution contribution of the MCP TOF (a.u.) 10

11 Relative Efficiency: ε r =N X /N TOF Isobutane C 4 H 10 ρ ~ 2.51x10-3 g/cm 3 OctaFluoroPropane C 3 F 8 ρ ~ 8.17x10-3 g/cm 3 1,0 0,9 0,8 C 4 H 10 - Isobutane 12 C 16 O 1,0 0,9 C 3 F 8 - OctaFluoroPropane 12 C 16 O 0,7 0,8 Efficiency 0,6 0,5 0,4 0,3 0,2 0,1 0, Energy (MeV) Efficiency 0,7 0,6 0,5 0,4 0,3 0, Energy (MeV) 16 O 40 MeV ε ~ 90% 12 C 14 MeV 16 O 130 MeV 12 C 45 MeV 11

12 New Focal Plane Detectors : Why? Atomic number Efficiency and mass resolution 40 Ar 96 Zr Efficiency Mass separation (1/A) Mass resolution (ΔA/A) SED Large energy straggling for slow moving heavy ions due to the detector windows 12

13 Working principle of Se-D A. Drouart et al., NIM. A477, 401 (2002)

14 SED small area prototype LPMWPC ASIC electronics Two Gas32 cards 80 Se MeV X and Y positions: October

15 Preliminary design of the SeD Se - D 31 Gas16 boards for the X anode Emissive foil Coils field rings Back plate omitted for clarity mm mm Beam mm

16 SeD - Electronics readout 16 PPAC wires 16 PPAC wires 2 nd prototype SeD PPAC readout module Gassiplex 16 channel ASIC Preamp Shaping amp Track and hold Analog multiplexed output 8 GAS16 boards 128 PPAC wires four connections. 16 channels - time multiplexed onto one analogue signal x 8 GAS16 board one 16 channel Gassiplex ASIC Clock + readout controls Analogue V4FADC board 8 x 12 bit FADC 50Mhz Analogue 10 x LVDS links GAS16 board one 16 channel Gassiplex ASIC 5Mhz readout clock ~3us 10 ADC samples per channel average of four recorded. PowerPC in the FPGA formats data Ethernet link to MIDAS in PC 1khz event rate. Data readout from FPGA Register and memory access. Xilinx FPGA XC4VFX12 Operates the Gassiplex control and readout. FADC conversion and data storage 1Gbit Ether Trigger JTAG FPGA re-programming

17 Gas16 board DL Connections Existing to ASICs the chips : Gassiplex Connections to the FADC (Gas16) board PPAC board 3 cm One Gas16 card (with 1x16 Gassiplex ASICs per card) to read 16 PPAC wires For each channel: Preamp + Shaping Amp + Track & hold 6 cm

18 PPAC DL Anodes X grounded (16 wires) + Cathode HV ~600V (trigger for Gas16 RO) + Anode Y grounded (16 wires) Analogic output of the Gas16 bord: Gas16 boards

19 Flash ADCs -ASIC readout module Ethernet link to MIDAS Clock + readout control External trigger Eight input channels Analogue signal from the ASIC (time multiplexed 16 channels)

20 Summary New PPAC for the PRISMA spectrometer have been assembled and tested with α particles; two days of beam-time (18th-19th Dec, 2007) have been allocated by the LNL PAC for their in-beam commissioning; Improved sensitivity and efficiencies for light charged nuclei; A large SeD detector is being designed also for PRISMA by a UK collaboration The electronics for individual wire readout has been Daresbury Laboratory and is currently being tested; Next stage: couple several V4FADC boards together and synchronised via a metronome.