Boutachkov, P.

Cappellazzo, M.

Gregor, E.

Jolie, J.

Koenig, W.

Kojouharov, I.

Müller-Gatermann, C.

Pfeiffer, M.

Pietralla, N.

GSI Repository

Fast Timing with DSSSD DetectorsP. Boutachkov∗1, E. Gregor1,2, N. Pietralla1, I. Kojouharov2, W. Koenig2, M. Pfeiffer3, M.Cappellazzo3, C. Mu¨ller-Gatermann3, and J. Jolie31TU Darmstadt, Germany; 2GSI Darmstadt, Germany; 3IKP, University of Cologne, GermanyThe NuSTAR HISPEC slowed down beams project atFAIR aims to produce rare isotopes with energies of 10MeV/u and less. The setup requires Time of Flight (ToF)information to determine the ion velocity, energy loss forZ identification and beam tracking for scattering angle re-construction [1]. A timing resolution ofΔT∼100 ps, posi-tion resolution of the order of a mm and energy resolutionof ΔE/E∼1% is required [1]. Due to the low beam energy,the number of detectors should be kept to a minimum. ThinDouble Sided Silicon Strip Detectors (DSSSD) provide en-ergy loss and position information, while their use as fasttiming detectors was not extensively studied. A combina-tion of commercially available DSSSDs and a new 16chfast pre-amplifier developed at GSI was investigated. Thesystem was cooled to -17◦C in order to reduce the detectornoise, improving the time resolution.A 5x5 cm2, 40 µm DSSSD model W1(DS)-40 9G pro-duced by Micron was glued on a copper frame. TheDSSSD has 16×16 x-y strips. They are bonded on one sideonly. A 16ch low power pre-amplifier based on BGA2712amplifiers by NXP Semiconductors was attached to theDSSSD [2]. The detector and the pre-amplifier were cooledwith a refrigerating machine and a two-stage Peltier cooler.A picture of the detector and the fast pre-amplifier mountedin the cooling frame is shown in Figure 1.The detector performance was studied with a 48 MeV12C beam produced at the Cologne FN-Tandem Accelera-tor [3], where the DSSSD time resolution was measuredrelative to a transmission Micro-Channel Plate detector(MCP) [4]. The energy of 48 MeV was sufficient for the12C beam to punch through the thin DSSSD.As mentioned above, the detector was cooled to -17◦C.The signal amplitude and rise time varied along the lengthof the detector strips. The fastest rise times (10% - 90%) oforder of 2 ns were measured for the pixels close to the stripreadout contact. Such a signal is shown in Figure 2. TheRMS noise after the fast pre-amplifier was in the order of0.3 mV. The signal rise time and noise level indicate that aresolution better than 100 ps can be reached.For timing measurements, the fast pre-amplifier wasconnected to a 16ch leading-edge discriminator, while theother side of the DSSSD was read out with a MesytecMPR-32 charge sensitive pre-amplifier. A CAEN 1290ATDC with 25ps LSB was used to measure the ToF betweenthe MCP and the DSSSD detector. A FWHM∼0.4 ns wasobtained for the DSSSD time resolution after subtractingthe contribution from the MCP.The difference between the expected and the measured∗This work was supported by NAVI, Helmholtz Association NuclearAstrophysics Virtual Institute.time resolution was attributed to the variation of the signalrise time along the detector strips and high discriminatorthresholds. The latter was due to a technical limitation ofthe fast discriminator used in the measurement.Improvement of the cooling system in order to reachlower temperatures, will lead to rise times below 2 ns. Thefaster rise times and a readout from both sides of the detec-tor strips should lead to resolutions better than 100 ps.Figure 1: An assembly of the 40 µm DSSSD and the 16chpre-amplifier mounted on the cooling frame.-14 -12 -10 -8 -6 -4 -2 0 2 4 6 8-16-14-12-10-8-6-4-202t[ns]V[mV]Figure 2: A fast pre-amplifier signal from a pixels close tothe strip readout contact.References[1] P. Boutachkov et al., GSI Scientific Rep. (2007) 215.[2] W. Koenig and J. Pietraszko, GSI Scientific Rep. (2008) 218.[3] M. Pfeiffer et al.,“A new Detector Testbed for future FAIRbased Slowed Down Beam Setups at the Cologne FN-TandemAccelerator Facility”, GSI Scientific Rep. (2012).[4] P. Boutachkov et al., GSI Scientific Rep. (2008) 236.GSI SCIENTIFIC REPORT 2012 PHN-ENNA-EXP-53183

Fast Timing with DSSSD Detectors

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Fast Timing with DSSSD Detectors

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