Beam Halo Monitor for the European XFEL Alexandr

Beam Halo Monitor for the European XFEL Alexandr Ignatenko Unwanted Beam Workshop Humboldt-University Berlin, Erwin-Schrödinger-Zentrum December 17 -18, 2012

Overview Ø BHM concept ª Aims and requirements ª Sensors Ø BHM @ FLASH ª Description ª Operation experience ª FLASH II Ø BHM @ XFEL ª Injector dump ª Main dump Ø Summary 2

BHM concept Aims and requirements • Part of the dump diagnostics • Supports safe beam dumping, signals fast upon dangerous conditions • Ensures that the beam and also the beam halo stay inside the beam pipe • High radiation tolerance • Capability to detect low enough charges 3

Sensors 1. p. CVD diamond Dimensions 12× 0. 3 mm 3 Metallization: 10× 10 mm 2 50/50/200 nm Ti/Pt/Au 2. Single crystal sapphire (Al 2 O 3) Cut [0001] Dimensions 10× 0. 3 mm 3 Metallization: 8× 8 mm 2 50/50/200 nm Al/Ti/Au 4

Diamonds Current-voltage characteristics A sensor assembled for tests CCE vs dose at 200 V Polarization Pumping with a 90 Sr A < 3 MBq 5

Radiation tolerance 10 Me. V electron beam @ S-DALINAC Predominant pumping Predominant signal degradation Moderate signal degradation up to 7 MGy 6

Sensor tests at PITZ 14. 5 Me. V electron beam, bunched Diamond sensor installed in vacuum inside the beam pipe x. RMS=3. 36 mm y. RMS=3. 29 mm Moving the sensor through the electron beam Bunch charge 1 p. C – 1 n. C: charges 1 -2 p. C hitting the sensor can be detected EMI did not disturb operation 7

Sapphires Signal as a response to a single MIP is too low to for detection Signal as a response to particle flux from 90 Sr: estimated CCE 2 -3 % 8. 5 Me. V electron beam @ S-DALINAC 30 % of the initial value of the signal after 10 MGy 8

BHM @ FLASH Description Free-electron Laser in Hamburg (FLASH) Max. electron beam energy Max. bunch charge Macro pulse frequency Max. macro pulse length Pulse frequency Peak current Peak power Pulse duration (FWHM) 1. 25 Ge. V 1. 2 n. C (3 n. C) 10 Hz 800 µs 1 MHz 1 - 2 k. A 5 GW 10 -70 ps 9

Dump line Electron beam pipe

Bias voltage and readout scheme Tunnel 4 m 55 -60 m Counting room 11

Operation experience The BHM @ FLASH has been commissioned in Sept. 2009 ADC clock Raw signal from a sensor Shaped signal from a sensor Digital signals from the BHM sensors as a response to 30 bunches 12

Signal from a diamond sensor as a function of beam position Signal from a sapphire sensor as a function of beam position Sweeping frequency 1. 1 Hz Signal from a sapphire sensor in the frequency domain 13

Calibration of the BHM Energy 700 Me. V 1 bunch per train (40 p. C to 1 n. C) Quads switched off Sweeper on, radius of 55 mm Beam centered (as good as possible) in the dump section

Sweeping Signals from the BHM sensors (in V) as a function of beam position beam(as position read out (reconstructed) from the “in-air” BPM) 16

Maximal signal among all on the circle, each point is an average for the measurement period Full range of signals for each measurement period for a diamond (left) and a sapphire (right) 17

Fits for a diamond a sapphire 3 ranges: linear, nonlinear, saturation Bunch charge = F -1(Signal) Diamond (UR) Sapphire (R) Low charges <50 p. C Low charges <90 p. C (6. 624 e-02)*x + (3. 140 e-16) (1. 403 e-02)*x + (3. 580 e-02) Middle charges >50 p. C & <113 p. C Middle charges >90 p. C & < 690 p. C (2. 070 e-06)*x 3 + (-6. 704 e 2 04)*x + (6. 991 e-02)*x + (1. 267 e+00) (2. 533 e-09)*x 3 + (-8. 697 e-06)*x 2 + (9. 022 e-03)*x + (5. 547 e-01) High charges >113 p. C High charges > 690 p. C (0)*x + (3. 623 e+00) (0)*x + (3. 472 e+00)

BHM @ XFEL Layout of the XFEL Max. electron beam energy Bunch charge Macro pulse frequency Max. macro pulse length Pulse frequency Peak current Max. average beam power 17. 5 Ge. V (20 Ge. V) 1 n. C 10 Hz 600 µs 4. 5 MHz 5 k. A 20 GW 19

Injector dump BHM position is right in front of the dump The sensors position outside the beam pipe BHM will provide signals to the MPS 20

Main dump Electron beam Dump The sensors position outside the beam pipe BHM ensures that the beam and halo fits into the pipe downstream the diameter step Readout electronics is in µTCA standard. BHM will provide signals to the MPS Direct calibration is not possible. It will be based on 21

Summary 1. The BHM system based on artificial diamond and sapphire sensors has been commissioned in Sept. 2009 and is in operation at FLASH 2. The sensors applied are capable to withstand doses up to several MGy 3. Diamonds are capable to detect charges of 1 -2 p. C 4. The BHM system monitors the beam halo with different sensitivities. It signals when the beam approaches the sensors 22

Acknowledgements Colleagues: N. Baboi, H. Henschel, O. Hensler, W. Lange, W. Lohmann, D. Nölle, M. Schmitz, S. Schuwalow, K. Wittenburg DESY Hamburg & Zeuthen University of Hamburg S_DALINAC, PITZ, ELBE crews Thank you for your attention!