Ingrid-Maria Gregor Der Silizium Recoil Detektor für HERMES Technisches Seminar DESY Zeuthen 8. April 2003 m Introduction m HERMES at DESY Hamburg m What do we want to measure ? m Recoil Detector Overview m Silicon Recoil Detector m Principle m First measurements m Zeuthen activities m Summary and Outlook

8. April, 2003Ingrid-Maria Gregor HERA at DESY Hamburg

8. April, 2003Ingrid-Maria Gregor HERA with polarised beam ã spin of electrons are “all” parallel to one axis ã HERMES is target experiment, but beam is not stopped in its region

8. April, 2003Ingrid-Maria Gregor The HERMES Spectrometer ã yellow: gas target ã red: tracking detectors 4 ã green: particle identification ã blue: calorimeter HERA Measurement of Spin

8. April, 2003Ingrid-Maria Gregor The Polarised Internal Gas Target ã years longitudinal polarised ã since 2002 transversal polarised

8. April, 2003Ingrid-Maria Gregor But what do we do there? ã nucleons consist of quarks and gluons ã spin of the nucleon: known to be 1/2 ã how contribute the different constituents to the spin? NUCLEON ã from quark parton model: quarks should carry largest part (0.6) ã EMC 1988: quark contribution only 0.12

8. April, 2003Ingrid-Maria Gregor And how do we measure ? ã deep inelastic scattering (DIS) ã polarised electron interacts only with quark of oposit spin ã by switching the polarisation asymmetries can be measured

8. April, 2003Ingrid-Maria Gregor Inclusive... semi-inclusive.... exclusive ã inclusive ã semi-inclusive ã exclusive want to take a closer look here recoiling proton low momentum

8. April, 2003Ingrid-Maria Gregor Generalised Parton Distributions ã exclusive reactions,e.g. are becoming a promising and powerful experimental tool to investigate the spin structure of the nucleon ã sdfrlskdfjlskdfslkdfjslkdfjsf are becoming a promising and powerful experimental tool to investigate the spin structure of the nucleon ã a unified theoretical framework describing inclusive and exclusive reactions at the same time has been obtained Generalised Parton Distributions è Generalised Parton Distributions

8. April, 2003Ingrid-Maria Gregor The Recoil Detector Position of Recoil Detector ã problem: with the acceptance of HERMESwe can not measure the recoiling proton ã problem: with the acceptance of HERMES we can not measure the recoiling proton

8. April, 2003Ingrid-Maria Gregor 3D Model of the Recoil Detector

8. April, 2003Ingrid-Maria Gregor 50<p<1400 MeV/c 0.1< q <1.35 rad The Recoil Proton Spectrum ã MC simulations ã kinematic distribution: recoil proton momentum versus polar angle ã silicon detects low momentum recoil protons ã SciFi is more suited for higher momentum protons proton momentum polar angle

8. April, 2003Ingrid-Maria Gregor Silicon Detector  to detect protons from DVCS and to reject events with intermediate  resonance ã uses energy deposition to determine momentum ã 2 layers of silicon ã 16 double sided Si sensors (TIGRE)  300 m thickness  758 m strip pitch ã p min 135 MeV/c   acceptance: rad

8. April, 2003Ingrid-Maria Gregor Principle of Silicon Detectors + - D t~10ns ã fully depleted pn junction for particle detection ã signal size is depending on particle energy

8. April, 2003Ingrid-Maria Gregor Bethe Bloch (1) ã energy deposition can be parametrised with Bethe- Bloch formalism 1/ 2  for low momentum: dE/dx falls like 1/ 2 ã minimum = minimal ionising particle = MIP ã rises very slowly for larger momenta

8. April, 2003Ingrid-Maria Gregor Punch Through Points  dependence of E 1 on E 2 which is characteristic for each particle type => PID ã low initial energy: particle stopped in first layer ã punch-through point 1: gets stuck in layer 2 ã punch-through 2:both layers are passed -> total energy deposition decreases

8. April, 2003Ingrid-Maria Gregor Bethe Bloch (2) ã huge dynamic range to be detected ã up to about 100MeV : proton stuck in Si ã >130 MeV: Si passes both layers ã to get energy information: analog readout chip  1/ 2 region

8. April, 2003Ingrid-Maria Gregor Helix  0.8 m m CMOS process â 10 MHz sampling frequency â 128 input channels â Analog pipeline 141 cells deep â Preamp-Shaper good noise char. â Radiation tolerant 220 krad. â Dynamic range â +/- 40 fC or +/- 10 MIP â required: +/- 280fC

8. April, 2003Ingrid-Maria Gregor Memory Pipeline channel number cell (128+trailer) read

8. April, 2003Ingrid-Maria Gregor Readout Conceptual Design ã analogue frontend readout chip with large dynamic range necessary ã HELIX dynamic range is “only” 10 MIP ã charge division by capacitive coupling readout ã “poor man’s solution” -> much better than new design ã tested with charge directly injected into  one minimal ionising particle (MIP) creates electron/hole pairs in 300 m silicon

8. April, 2003Ingrid-Maria Gregor Charge Injection

8. April, 2003Ingrid-Maria Gregor Readout Conceptual Design 22 ã dynamic range â of low gain Helix: ~10MIP â of high gain Helix: ~40MIP (10 pF) â ~70MIP (5 pF) 10 pF

8. April, 2003Ingrid-Maria Gregor First Prototype ZEUS hybridsensor 23 â sensor: TIGRE, 99 x 99 mm 2, double sided  300 m silicon thickness  strip pitch: 758 m  readout pitch: 758 m  readout: HELIX chips, 0.8 m CMOS â 128 channels â sensor: TIGRE, 99 x 99 mm 2, double sided  300 m silicon thickness  strip pitch: 758 m  readout pitch: 758 m  readout: HELIX chips, 0.8 m CMOS â 128 channels

8. April, 2003Ingrid-Maria Gregor Testbeam at DESYII â carbon fibre generates Bremsstrahlungs beam â metal plate --> converts into electron/positron beam â dipol magnet spreads beam out â magnet used to select energy (1-6GeV) â to check if charge sharing results in reasonable values when tested under realistic conditions â to scale previous charge injection studies to “real” MiPs

8. April, 2003Ingrid-Maria Gregor Reference Telescope â Zeus testbeam was used â system with three different reference detectors â device under test (DUT) movable in all three directions â scintillators for trigger â data is stored as digitalised ADC counts

8. April, 2003Ingrid-Maria Gregor Reference Telescope â sensor: 32 x 32 mm 2, single sided, p-side strips  300 m silicon thickness  strip pitch: 25 m  readout pitch: 50 m  readout: VA2 chips, 1.2 m CMOS â 128 channels

8. April, 2003Ingrid-Maria Gregor Testbeam Picture

8. April, 2003Ingrid-Maria Gregor Energy Loss Distribution high gain channel: no Gaussian noise, Landau fit S/N:6.5 â energy loss distribution for 1GeV electrons in 300 um silicon (one strip, 10pF coupling, n-side) â Gaussian distributed noise is cut (threshold = 3 x noise) â Landau fit --> signal size = most probable peak â signal to noise ratio S/N = 6.5

8. April, 2003Ingrid-Maria Gregor Comparison p-Side and n-Side ã both sides were tested with 1 GeV electrons ã same channels were addressed ã signals size of both sides are within +/- 5% ã p-side ~100ADC counts, S/N = 7.8 (1MIP) ã n-side ~ 80ADC counts, S/N = 6.5 (1MIP) ã small S/N -> due to large capacitance of strips ã 20% difference -> due to large difference in total capacitance of strips

8. April, 2003Ingrid-Maria Gregor Difference p-Side and n-Side ã can be explained by the difference in the strip capacitance ã C virt : total capacitance of readout (high gain Helix, low gain Helix, fanout) ã calculating this network, a difference of 17% in the signal size is expected

8. April, 2003Ingrid-Maria Gregor Present Status of Mechanical Design SciFi Connector Holding Structure Scattering Chamber Target Cell HERA Beamline TIGRE Sensors Hybrid Cooling Collimator

8. April, 2003Ingrid-Maria Gregor Summary Si-Detector ã HELIX 3.0 chosen for readout. ã First prototypes have been constructed and tested in test beam. ã Readout using charge division has been shown to work. â 50% charge collection due to large sensor capacitance. â S/N for 1 MIP is 6.5 (n-side) â With a 5 pF coupling capacitor, particles depositing 140 times the energy of a 1 MIP particle can be measured! ã first “real hybrid” is in production ã test stand in Zeuthen for laser tests and electrical tests

8. April, 2003Ingrid-Maria Gregor Zeuthen Activities ã coordination of project ã testbeam ã laser tests ã chip acceptance test ã parameter tuning ã hybrid testing ã ACC ã..... ã coordination of project ã testbeam ã laser tests ã chip acceptance test ã parameter tuning ã hybrid testing ã ACC ã..... ã Wolf-Dieter Nowak ã James Stewart ã Wolfgang Lange ã Arne Vandenbroucke ã Mikhail Kopytin ã Ivana Hristova ã me ã with lots of help from the technical staff !!! ã THANK YOU !!