MPE-PE Technical Meeting Oliver Stein

1. Diamond based fast particle detectors for LHC machine protection, experimental setup and measurements at the BTF, Frascati. MPE-PE Technical Meeting Oliver Stein

2. Outline. • Motivation • Introduction • Ionisation Chamber Beam Loss Monitors (icBLM) • Diamond Beam Loss Monitors (dBLM) • dBLMcharacterization experiments • Introduction Beam Test Facility (BTF), Frascati, Italy • Setup layout • First measurement • General results • Conclusion

3. Motivation. • The detection of beam losses is important for the safe operation of the LHC and its • pre-accelerator complex at CERN! • Beam losses are THE indicator for the existence of an (unacceptable) danger in the accelerators: • Orbit offsets. • Equipment failures. • Beam instabilities. • The installed Beam Loss Monitors (BLM) are connected to the Beam Interlock System •  Losses above the defined thresholds cause a beam dump!

4. Introduction, ionization chamber BLM. • Ionization chambers are used as the standard beam loss monitors (icBLM) in the LHC. • N2 filled cylinder (1.1 bar). • 60 cm length. • Parallel electrodes (0.5 cm). • 40 µs time resolution (half turn of LHC beam). • More than 3600 icBLMsinstalled. icBLM Electrode setup inside an icBLM icBLMs in IP6

5. Introduction, diamond based BLM. • What happens within 40µs? • Solid state BLM type: diamond based BLMs (dBLM). • 1.5 ns rise time resolution (5 ns FWHM)  bunch by bunch resolution. • Large dynamic range (few – 1010MIPs). • dBLM should detect fast beam losses during LHC operation and help to understand the underlying loss mechanisms. • Abort gap monitoring • Stable beams • Ramp/squeeze • Injection • Extraction 50 ns Courtesy of M. Hempel Courtesy of M. Hempel

6. Experience with dBLMs @LHC • Goal: Making the dBLMs fully operational and improve their usability for Post Mortem checks! • Analysed data from previous LHC runs show linear response behaviour for certain loss intensities. • Further Steps: • Better understanding of the detector. • Detector response (linearity). • Efficiency. • Saturation limits. • Detection limits. • Development of DAQ system. Linear?

7. Beam time from 24.03.2014 to 01.04.2014@ BTF, Frascati. BTF • Detectors: • 3 x 100 µm dBLM (ø 5mm) special detectors used in HiRadMat experiments 2012. • 2 x 500 µm dBLM (10 mm x 10 mm) LHC dBLMs. • Characterization experiments with high intensity electron beams (105 – 109e-/bunch): • Response measurements. • Voltage scans for charge collection distance (CCD) calculations.

8. BTF. • Beam Test Facility is a beam line at the DAFNE accelerator complex. • Single bunches can be kicked into the transfer line to the BTF hall (repetition rate 1Hz, (up to 50 Hz)). • Operation modes: • High intensity, primary beam, ( 105 - 5 x 109 e-per bunch@ ~ 500 MeV, bunch length ~10ns). • Low intensity, secondary beam ( 101- 105e- per bunch@ < 450 MeV). • The beam intensity can be adjusted by using scrapers and a spectrometer magnet. • Wall current monitor (WCM) to measure bunch intensities (> 107 e-/bunch). BTF WCM Spectrometer magnet Target Kicker magnet DAFNE LINAC

9. Setup layout. Beam window icBLM Collimator dBLM For max. fluence, the detector was placed directly in the beam. IcBLM was used as reference. Collimator, to intercept particles, which did not pass through the detector. Logging WCM data for additional information. Beam window Collimator icBLM dBLM Copper Lead WCM e-

10. Setup alignment. Beam window icBLM Collimator dBLM Achieved alignment precision: Vertical angle : < 0.5 mrad Horizontal angle: < 0.25 mrad 40 cm 60 cm 380 cm Collimator Spirit level Beam window Laser

11. Setup shielding. • To minimize the radiation in the experimental hall additional shielding was applied. • Around 500 kg of lead bricks were used. • No significant higher radiation levels were observed during the measurements.

12. Cabling of control / read out hardware. Experimental hall Control room Att. / Shunt Scope Collimator dBLM WCM icBLM Keithley CERN Laptop XY- Table BTF computer HV Rack

13. Alignment with beam. The X-Y-table was used for precise detector positioning (Δx: 0.5 mm Δy: 0.5 mm). Alignment scans were performed for every new installed detector and repeated from time to time. WCM allowed to normalize the icBLM and dBLM signals to the beam intensities. Beam position was stable within 1mm (hardware uncertainties).

14. Example scope signals and WCM vs. icBLM The data acquisition was triggered by BTF trigger wit 1 Hz repetition rate. Due to the high beam intensities attenuators (-20 dB, -40dB) and a 1Ω shunt system were used. For higher statistics, multiple measurements (~50) were performed for the same set of parameters. Data analysis showed linear ratio between WCM and icBLM.

15. Summary of the beam time. • Setup worked very well. • Mostly stable beam operations and high availability of the facility. • Close collaboration with the BTF and LINAC team. • Measurements were performed within a intensity range of 105 to 109 electrons per shot. • Main intensities in the order of 108to 109 . • Used detectors: 3 x 100 µm dBLM (ø 5 mm) (H1,H2,H3). • Duration of measurements: • Alignment scan 60 - 90 min. • Voltage scans 90 -120 min. • 55 Gb of data recorded (~25 000 data sets). • Results of the dBLM characterization will be presented by Florian Burkart: • Experimental results from the characterization of diamond detectors with high intensity electron beam

16. Thank you for your attention!