1. TESLA Test Facility TTF II Review Meeting, Salzau, January 2003 Introduction to the Electron Beam Diagnostic Session Dirk Nölle DESY, MPY 9-2579 Dirk.Noelle@desy.de

2. TESLA Test Facility Overview of the Session D. Nölle; Introduction M. Wendt; Status of Beam Position, Charge and Phase Monitors K. Honkavaara, A. Chanci; OTR Systems M. Koerfer; Optical Fibre Dosimetrie M. Jablonka; Toroid Protection System

3. TESLA Test Facility Challenges of the Diagnostics LINACs are Open Loop Systems –Beam Parameters change and have to be measured in different Parts of the Machine; –Measurements need Single Bunch Resolution over the whole Bunch Train. –Pulse to Pulse and Bunch to Bunch Fluctuations have to be detected. High Duty Cycle Single Pass Machines can destroy Themselves –Radiation Damage, Heat Load –Need a very sensitive fast acting Protection System. –Threshold and Reaction Time is determined by the most sensitive Component (  3  s). Ultra short compressed Electron Bunches –How to measure bunch lengths in the 100 fs Regime? Strong Dependency of Electron Beam and SASE Performance –Characteristics (Intensity, Spectrum, Pulse Length) –FEL Intensity shows statistical fluctuations –Operator needs FEL Parameters and their Statistics.

4. TESLA Test Facility LINAC - Storage Rings LINAC Pulsed System with large Fluctuations Triggered Electronics have to take Pulses with the rep. Rate of the Bunches. (9 MHz for TTF II) Storage Rings Closed loop Equilibrium System Watch beam Parameters under stable Conditions. Systems can be much slower and can average over long Times. Precise Measurements in the Frequency Domain.

5. TESLA Test Facility... further Complication What do Monitors see: –Mean value of charge per bunch –Mean value of position per bunch –Projected emittance –... What is contributing to the FEL process? Longitudinal Charge Distribution measured at TTF I Lasing Fraction

6. TESLA Test Facility Areas of Special Interest for Diagnostics Remark: TTF has everything, a big Machine also has, but everything concentrates in a limited Area ! bunch compressors dump Laser superconducting cavities rf-gun FEL beam undulatorcollimator

7. TESLA Test Facility „Butter and Bread Diagnostics“ Charge

8. TESLA Test Facility Fast Toroid System –Single Bunch Resolution –Time Constant < 110 ns –Bunch Rep. Rate = 9 MHz –Range 0.1 to 5 nC –Accuracy  10 -3 Need to Measure –Charge –Charge Distribution of the Bunches in the Beam Pulse –Transmission along the Machine T1T8T2, T3T4,T5T6, T7T9 T10

9. TESLA Test Facility „Butter and Bread Diagnostics“ Charge Beam Position

10. TESLA Test Facility Warm Parts of TTF II; Striplines, Pickups: Use a modular electronics system for all BPMs –Single Shot, Single Bunch Readout –External Trigger –Variation of the Beam Position over the Macro Pulse Striplines installed and aligned inside the Quads (Res. < 30 µm, 34 mm Pipe) Button Arrays (8 Pickups/Monitor) for the BC (manage large variation of Beam Position) Pickups in the Diagnostic Blocks between Undulator Sections and 2 inside each Undulator (Res.  10 µm) In the Accelerating Modules : Cold Cavity BPMs Cold Reentrant Cavity in ACC1 (by CEA)

11. TESLA Test Facility „Butter and Bread Diagnostics“ Charge Beam Position Transverse Electron Distribution

12. TESLA Test Facility Screens (OTR, YAG Screens) –Beam Size (typical O(100µm)), Measure Emittance, Energy Distribution –Resolution  20 µm –Interceptive –Low Damage Threshold (3 – 10 bunches) (Presentation by A. Chianci, this Session) Extraction of Coherent FIR Radiation –Measurement of Compression and Bunchlength OTR Station for TTF II Screens

13. TESLA Test Facility Wire-Scanner Wire Scanners Machine: Modified CERN Scanners with a „V Fork“ and 45° Assembly with Respect to the Beam  x and y measurement with one device  combined with an OTR in the same housing Undulator: New developed Type with an unidirectional Drive Unit (Presented by M. Sachwitz; Undulator Session) e-e- OTR WS OTR/Wirescanner Chamber

14. TESLA Test Facility „Butter and Bread Diagnostics“ Charge Beam Position Transverse Electron Distribution Dark Current

15. TESLA Test Facility Dark Current Dark Current is emitted in RF Structures –Fills every RF-bucket –Produces losses along the machine –Contributes to Cryo-Load Main Contribution emitted by the Gun –Increases with the age of the cathode –Cathode has to be changed if DC exceeds a given threshold Measure DC by Sum Signal of a Reentrant Cavity BPM –Resolution O(500 nA) –Redesign for a 34 mm Beam Pipe will be started ASAP Dark Current at TTF I: Sum Signals of Reentrant Cavity BPMs sampled between the Laser driven Bunches

16. TESLA Test Facility „Butter and Bread Diagnostics“ Charge Beam Position Transverse Electron Distribution Dark Current Phase

17. TESLA Test Facility Phase Due to magnetic Bunch Compression Energy Fluctuations turn into Phase Fluctuations Beam Signal mixed with the (1.3 GHz) Master provides a Signal proportional to the Beam Phase Time Of Flight Measurement: Resolution  0.5° or 1 ps (tested with TTF I Stripline as a Pickup) Ring Electrode installed in a „Thick Flange“ –Broadband, Position independent Signal –One installed after the Gun, each magnetic Chicane (BCs and Collimator)

18. TESLA Test Facility „Butter and Bread Diagnostics“ Charge Beam Position Transverse Electron Distribution Dark Current Phase … this is not sufficient for a SASE Machine! More detailed Information provided by M. Wendt and K.Honkavaara/A. Chianci later this session

19. TESLA Test Facility Bunchlength and Compression: Scale: Resolve Structures of 100 fs and less Qualitative: Optimization of the Compression –Phase Tuning to maximize the coherent FIR Emission from the Beam. –Emission  n 2 for  s  –Use of simple Pyro-Detectors in the FIR Quantitative: Measurement of Bunch Length –Use coherent FIR Radiation and Autocorrelation Methods. –Transverse Mode Cavity (integrated Streak Camera) –Electro-Optical-Sampling  presented in the ACC7 Session from yesterday

20. TESLA Test Facility Protection Systems SASE LINAC: –„Big Welding Machine“ –„Big X-Ray Tube“ Therefore: –Need very fast Interlocks to avoid Mechanical Damage. –Need continuous Monitoring to minimize Radiation Damage. Transmission and Loss based Systems –Thresholds given by most sensitive Component (Undulator) –Fast and Slow Systems –Reaction Time by „Worst Case Events“ (and Signal Travel)

21. TESLA Test Facility Slow Loss Monitoring Systems TLDs –TLD crystals located at sensitive regions (undulator section) –Document the Irradiation Profile over long Times –Data on a weekly Basis Optical Fibers used as Dosimeters –Small Opt Fiber Coils installed close to the Undulator Gap –Transmission Decrease of the Fiber due to Radiation Damage –Allows Avoid Operation Modes with medium high losses Correlation of Dose Measurement with operation Modes –Reaction Time  1h Talk by M. Körfer, this session

22. TESLA Test Facility Fast Beam Inhibt System Modular System made of fast Beam Interlock Concentrators (BIC) BIC Modules can be cascaded, Input Mask and Event Status controlled by PLC Interlock Inputs: Different Systems using Same Interface and Communication Protocol: Protection Systems, RF, Fast Acting Valves,.... Reaction Time for Fast Channels:  O(  s) Talk by M. Staack in the „Timing and Controls“ Session

23. TESLA Test Facility Transmission Based Protection System for TTF II Used for Beam Inhibit Charge Measurement only Inhibit Pairs for TTF II: T 1 – T 9 : Whole Machine (FEL Mode) T 1 – T 11 : Whole Machine (Bypass Mode) T 2 – T 6 : 2 nd System for both Modes T 6 – T 10 : Make sure the beam is send to the beam dump Pairs of Current Monitors + fast acting Interlock Electronics Detailed Information Presented in this Session by M. Jablonka, CEA Laser T1T8 T2,T3 T4,T5T6, T7 T9 T10

24. TESLA Test Facility Loss Monitor Systems  50 Fast Loss Monitors (Photomultipliers) at critical Machine Parts Used as fast input Channels for the Fast Beam Inhibit system PM Operation Panel of TTF I

25. TESLA Test Facility SASE Diagnostics Tolerances on Machine Settings are very tight!  Light Production has to be controlled and optimized by the Operator  Strong Interaction with Photon Diagnostics (Talk by R. Treusch) Operator needs to keep optimum Performance: –SASE Signal + Statistics –Radiation Spectrum (Pulse Length) (few modes only  high peak power, Operation Experience of TTF I) MCP detector Gold wire 250 µm SiC mirror SASE radiation U MCP has been calibrated for different voltage settings dynamic range: 10 7 Thin lines: Single Shot Spectrum Bold: Average over many Shots

26. TESLA Test Facility

27. Consequences of Budget Shortage Priorities: –Complete Vacuum System for the Maschine –Start with Commissioning of the Injector Get new stuff going with minimized effort (e.g.Toroids) Reuse TTF I Components (e.g. BPM Electronics, Cameras) –Complete Infrastructure required Technical Interlock System (BIS/BIS) Do everything that gets more expensive afterwards (Tunnel Holes) –Keep Developments running Try to allocate Budget to continue running delepoments and prototyping (e.g. BPM Electronics, OTR Stations, loss Monitors) –Still need moderate Budget for these aims