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CVD Diamond Sensors for the Very Forward Calorimeter of a Linear Collider Detector

This study investigates CVD diamond samples for use in the Very Forward Calorimeter of a linear collider detector. The samples were characterized using various surface treatments and metallization techniques. The resistance and current-voltage characteristics of the samples were measured, both before and after irradiation. Raman spectroscopy and photoluminescence analysis were used to analyze the diamond samples. The results show that the CVD diamond samples have potential for use as a detector in the Very Forward Calorimeter.

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CVD Diamond Sensors for the Very Forward Calorimeter of a Linear Collider Detector

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  1. CVD Diamond Sensors for the Very Forward Calorimeter of a Linear Collider Detector K. Afanaciev, E. Kouznetsova, W. Lange, W. Lohmann

  2. Diamond samples • Fraunhofer Institute (Freiburg) : • CVD diamond 12 x 12 mm • 300 and 200 um thickness • Different surface treatment : • #1 – substrate side polished; 300 um • #2 – substrate removed; 200 um • #3 – growth side polished; 300 um • #4 – both sides polished; 300 um • Metallization: • 10 nm Ti + 400 nm Au • Area 10 X 10 mm

  3. HV Diamond Keithley 487 N2 I(V) dependence – setup Measurements were done with Keithly 487 picoammeter • Extremely low currents => N2 atmosphere EM shielding • Average resistance ~(1013-1014) Ohm (ohmic behavior) • 3 samples from different groups have “non-ohmic” behavior and lower resistance (~1011 Ohm) Usual I(V) curve Non-ohmic curve

  4. ADC Sr90 delay PA diam. Scint. discr & PM1 Gate discr PM2 Charge Collection Distance (CCD) Qmeas. = Qcreated x ccd / L Qcreated(mm) = 36 e-h pairs • The samples haven’t been irradiated before these measurements • All data was taken 2 minutes after bias voltage applied

  5. CCD measurements results

  6. CCD – irradiation studies • The samples were irradiated with Sr-source with estimated dose-rate of about 0.45 Gray per hour • The total absorbed dose for all the samples was at least 5 Gy. • Bias field was set to 1 V/m • Irradiation was homogeneous over the sample area • Parameters monitored during the irradiation: • Sr-spectrum peak position • width of the peak (->noise) • current in HV-circuit • test pulse from a generator (-> electronics stability)

  7. CCD – irradiation studies – results Group #2 (substrate side removed). HV = 200V Group #3 (growth side polished). HV = 300V

  8. CCD – irradiation studies – results Group #2 (substrate side removed). HV = 200V Group #1 (substrate side polished). HV = 300V

  9. CCD – irradiation studies – results Group #3 (growth side polished). HV = 300V Group #4 (both sides polished). HV = 300V

  10. N (575) N (637) FAP 2_1 LO Phonon Si (770) FAP 4_2 Photoluminescence analysis -> no nitrogen, no silicon HeCd Laser Reference spectra

  11. Raman spectroscopy Resolution ~ 1 cm-1 Result= S(diam)/S(graphite)*1000 Result= S(diam)/S(graphite)*1000 Resolution ~ 1 cm-1

  12. FAP 2_1 FAP 4_1 Raman spectroscopyresults

  13. Removed substrate • Group#3 – removed substrate (300 mm -> 240 mm)

  14. Results and further studies • Group#2 in general can work as a detector • Raman spectroscopy + photoluminescence analysis -> no nitrogen, no silicon • Next steps: • Influence of the substrate side on CCD and stability • Homogeneity and linearity required for the application • Test beam (May 2004)

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