ERL YAG & OTR Profile Monitors

1. ERL YAG & OTR Profile Monitors D. Gassner, E. Pozdeyev 9-24-07 Outline AP Requirements OTR YAG Profile type breakdown ERL Layout Types of 6-way crosses Radiabeam - Integrating Beam Imaging System (IBIS) Plunger head Impedance Match Actuator & Viewing port Optical path Optics box & calibration Data Acquisition CosyEye Spec Process Variables What’s Left?

2. AP requirements (Low Energy 2.5 MeV Injection Transport / Dump) AP requirements (High Energy Ring 20 MeV) E. Pozdeyev 4-15

3. Optical Transition Radiation Maximum intensity at angle Use metal coated silicon wafer screens (V.L.) “The OTR screen is a better choice when a beam intensity integrated over a CCD frame (33ms) duration exceeds 1 nC/mm2”. Alex Murokh - Radiabeam

4. OTR Efficiency Number of vis. light photons per 10x10 μm2 area for 1 and 0.1 nC/mm2. It has to be scaled by light collection efficiency to get the real number of photons per CCD cell. Energy radiated by an electron and effective QE Typical CCD: Noise floor 10 ph-e-/pixel Can see 100-1000 ph-e-/pixel Depending on energy, light collection efficiency can be of the order of from <0.01 for low E to >0.3 at high E. From the presented curves, it is follows that 1 nC/mm^2 is the reasonable estimate. In a straight section at E=20 MeV, beam sizes are approx. sig_x~sig_y~0.2 mm. Therefore the charge per frame (might be a single synchronized shot) must be larger than In a bend at E=20 MeV, beam sizes are approx. sig_x~2-5 mm, sig_y~0.2 mm. Therefore the charge per frame (might be a single synchronized shot) must be larger than 1.3-3 nC For the 2 MeV injection line, the beam rms sizes are approx. sig_x~sig_y~3-5 mm. Therefore the charge per frame must be of the order of 20 - 50 nC. Lower light collection efficiency might call for a larger charge. However, because the image is large, it can be focused to decrease the area on CCD.

5. YAG:Ce Screens • Dynamic Range • YAG:Ce scintillator is a better choice under 0.1 nC/mm2 • Beam profiles & position at low intensities: 1nA – 1μA (EP) • Depends on camera, optics, resolution, etc. .. • 0.02pC/um2 saturation limit, Lumkin & ATF • Saint-Gobain YAG:Ce (0.18% Ce) product data sheet • Wavelength of emission 550nm (good for most CCD cameras) • Decay time 70ns(fast) • 0.1mm thick crystal, yield about 730 photons/electron • Intercepting measurement, semi-destructive, losses YAG:Ce Spectral profile A.Murokh, ATF YAG:Ce 0.1mm thick 3.5MeV, 2us pulsed beam A. Warner, Fermi, 2005

6. YAG crystal considerations pC charge per frame should be detectable at high energy. Tens of pC per frame should be detectable at a low energy. Saturation: At E=20 MeV and in a straight section, the maximum bunch charge cannot exceed Therefore, YAG crystal saturation can be a concern in straight sections at the high energy even if the bunch charge is 1.4 nC. In the bends, the horizontal size is larger by an order of magnitude (~2-5 mm). Therefore, saturation is not a problem if the bunch rep. frequency does not exceed the frame rate by more than an order of magnitude. Saturation is not a problem in the injection line, unless the bunch rep. rate exceeds the frame rate by approximately two orders of magnitude, which is not advisable considering the deposited power. “YAG Profile monitors will be used primarily for position measurement, not so much for beam size.” (V.L.)

7. ERL Profile Monitor Type Breakdown Combination YAG:Ce & OTR 3 Fixed locations injection line 5 Plunging locations in loop 1 Plunging in dump transport Wire Scanner 1 After 3rd dipole in loop, start of straight section Synchrotron light 4 At loop dipole ports Under discussion Laser wire scanner (high power profiles) Streak Camera Pepper-pot

8. ERL Injection Layout Flag 2 Flag 3 Flag 1 ERL Extraction/Dump transport ?

9. ERL Loop Layout Flag 4 Flag 3 Wire Scanner Dump Flag Flag 5 Flag 2 Flag 1

10. ERL Loop Vacuum Crosses 2 Types: Quad Doublet; quantity 4 in straight section, 2” beampipe, 2” cross, 4.5” flanges Quad Triplet; quantity 5 in arcs, 2” beampipe, 1.5” cross, 2.75” flanges

11. Radiabeam IBIS Radiabeam Contact - Alex Murokh formerly of BNL ATF IBIS - Integrating Beam Imaging System Custom Design features for ERL - E-10 Vacuum - Dual purpose - OTR & YAG (3 position) - Plunging parts to fit our existing vacuum cross & flanges - Optics for our beam parameters - Include multi-position ND filter - Impedance matching - Plunge from side to get camera off axis Standard Radiabeam IBIS Profile Monitor

12. Dual purposeThree position Plunger head

13. Impedance Matching Full retract position “squirrel cage” Not perfect: Cross geometry Vacuum conductance Slots in cage, need size details: beam perspective vacuum perspective Daresbury Solution

14. Actuator Detail &Viewing port Need external survey fiducials on actuator housing Survey can locate to 100um accuracy.

15. Radiabeam YAG Screen Profile Monitor Beam direction YAG Screen Optics Box Camera Lens filter Consider Faraday Cup Option: (move forward on this, consider design Impact, Ilan says scattering should not be an issue at these energies.) Will find out if copper is best material for mirror. 20MeV electron range in copper is about 1.12cm's (10.043/8.9)

16. Radiabeam Optics Box Radiabeam IBIS resolution: “Better than 20um” ERL Modifications Specify Camera Replace 3-motion lens: zoom focus iris With fixed lens & ND Filter wheel Calibration: OTR Fiducialized screen YAG Fiducialized mask Radiabeam will provide a simple alignment fixture to ensure decent mechanical to start. Need insitu alignment scheme? Rotatable flanges Survey fiducials on actuator body Better than 1 degree accuracy

17. YAG, OTR & Synchrotron Light DAQ Use Unibrain FireRepeater 400 To get camera data to 1394 Interface • - Dedicated image processing computer • Ethernet bandwidth is low • Image processing done on microIOC server Performance Questions (& Answers): - Desired frame rate? (Typical 1/30) (33ms frame rate OK) - Maximum acceptable delay? (between image acquisition and image analysis) Using it for closed loop feedback? (No Closed loop, delay not an issue) - Desired resolution (number of pixels/mm of the actual image) - Can the image be black and white ? (list trade off’s, DAQ should accept both types of cameras) - Constant image analysis, or is the user mostly interested in the image only? (TBD) Alternative DAQ: Mindready Sednet 1394, used at Diamond

18. Cosylab CosyEye microIOC tech-spec

19. EPICS YAG & OTR Process Variables Image data from camera Camera trigger & delay Integration time Camera gain Plunge control Plunge status Calibration lamp control ND filter control

20. What’s Left To Do? Finalize Radiabeam designs for loop devices Finalize Injection monitor design (2 locations) Locate Dump transport profile monitor position, use loop plunging device? Choose CCD camera & data transport method (FireWire or GigE) Choose DAQ solution: Determine frame rates from cameras Triggering capabilities Maximum data rate (cameras used simultaneously, etc . .. CosyLab questions, & Confirm CosyEye microIOC meets our needs MindReady Sed-Net PMC or VME FireWire interface. Other Profile Monitors: Wire scanner design Synchrotron Light Monitor design Pepper-pot design