Fast Detectors and Electronics for Nanosecond Time Resolved Experiments O. Leupold, H.C. Wille, I. Sergueev, M. Herlitschke, P. Alexeev, C. Strohm, W. Roseker FS-PE, Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany Avalanche Photo Diode Detectors General features of APDs 16 element APD detector Standard APD Excelitas 5x5mm2 100 µm thick Single element > ns time resolution > fast recovery time, < 2 ns > single photon counting > high count rates up to 108s-1 > high efficiency at energies < ~10 keV > semi-transparent´at energies > ~10 keV Typical pulse from APD / fast amplifier Efficiency of standard APD assemblies 600 µm ↔ 4 inclined APDs stacked 400 µm ↔ 4 APDs stacked 100 µm ↔ 1 APD Single APD Hamamatsu S5443 3mm diameter 30 µm thick Efficiency of ~15% at energy of ~73 keV due to extreme shallow angle of incidence on the 16 APDs Beam Data Acquisition Systems and Applications Nuclear Resonance Scattering on 193Ir at 72.9 keV Standard setup: Veto around t=0 needed, width usually >20 ns, max. 1 acquisition per pulse Time-to-Digital-Converter(TDC) [2] No veto needed Time resolution 100ps, in up to 5 channels Pulse repetition rate <5 GHz (might be limited by detector) Multiple events per sweep Bunch purity measurements also possible on specific main bunches Digitizer (ongoing project) [3] No veto needed, direct digitalization Event-based acquisition and pulse-height On-board data processing Fig.: Nuclear inelastic scattering from a 57FePt sample with 6.4 keV (Fe K-α) and 14.4 keV (inelastic scattering) levels TAC CFD MCA PC VETO Signal ADC This nuclear resonance - nuclear life time ≈ 8ns - was observed recently at the PETRA III beamline P01 Nuclear Forward Scattering (NFS) experiments were possible due to the fast APDs of the 16 element APD detector, which enables one to start time resolved measurements already about 3ns after the strong exciting SR pulse For more details see [1] Fig.: NFS on IrO2 at about 15 K exhibits pure quadrupole interaction: splitting ΔEQ ≈ 670 neV A small external field of 0.5T does not change the NFS pattern significantly Application in XPCS – distinction of one and two photon correlations Application in NRS – multihit events 4 photons 3 photons 2 photons 1 photon per bunch It was shown [4] that photon correlation spectroscopy on a bunch to bunch basis yields different results for 1-photon events and 2-photon events With the TDC 1- and 2-photon events can be distinguished by the puls width at fixed threshold time Exciting SR pulses FeBO3 single crystal in pure nuclear scattering geometry Experiment at ESRF / ID18 in 4 bunch mode threshold 1- photon event 2- photon event 1 photon per bunch 2 photons per bunch 3 photons per bunch 4 photons per bunch Pulse Width Distribution 1- photon events 2- photon events 3 and more photon events Events Fig.: NFS on Ir metal at two different temperatures exhibits no hyperfine interaction The time modulation at 13K and the decay faster than the natural lifetime at 300K are due to multiple scattering, which is more pronounced at low T References: [1] P. Alexeev, 2017 User meeting, Poster 306 [2] FAST ComTec GmbH, http://www.fastcomtec.com [3] Involved institutes and funding: DESY, ESRF, TU Kaiserslautern, BMBF, XFEL [4] Hruszkewycz, S. O., Sutton, M., Fuoss, P. H., Adams, B., Rosenkranz, S., Ludwig, K. F. J., Roseker, W., Fritz, D. M., Cammarata, M., Zhu, D., et al. (2012). Phys. Rev. Lett. 109. DOI: 10.1103/PhysRevLett.109.185502