ERL YAG & OTR Profile Monitors D. Gassner, E. Pozdeyev 9-24-07 Outline AP Requirements OTR YAG...
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Transcript of ERL YAG & OTR Profile Monitors D. Gassner, E. Pozdeyev 9-24-07 Outline AP Requirements OTR YAG...
ERL YAG & OTR Profile Monitors
D. Gassner, E. Pozdeyev 9-24-07
OutlineAP RequirementsOTRYAGProfile type breakdownERL LayoutTypes of 6-way crossesRadiabeam - Integrating Beam Imaging System (IBIS)Plunger headImpedance MatchActuator & Viewing portOptical pathOptics box & calibrationData AcquisitionCosyEye SpecProcess VariablesWhat’s Left?
AP requirements (High Energy Ring 20 MeV)
Beam Profile
Parameter Expected Value/Range Accuracy Resolution Comments
Beam emittance 2 – 10 μm, norm 30% 0.1 μm, norm ε=2 μm is nominal. Quad/Sol. scan. See next line.
Transverse Beam Profile
Size (rms): 0.1-5.0 mm. (Aperture. ±1.0 cm)
10% (LP) 5 μm (LP)High resolution is required for quad scan and beam matching. Required in the low power (LP). In the high power regime (HP), lower accy./res. can be sufficient.
Beam Halo Full aperture 30% 1 ppmWorking in the (low- and) high-power regime. A set of scanner wires with a BLM?
Longitudinal profile 50-150 psec 10 psec 2 psec Required at LP, highly desirable at HP.
Energy spread (dE/E) 1% (rms) 1e-3 2e-4 Required at LP, highly desirable at HP.
Beam Profile
Parameter Expected Value/Range Accuracy Resolution Comments
Beam emittance (slice)
2 – 10 μm, norm 30% 0.1 μm, normPepper pot in the injection line. Projected emittance will be larger than the slice emittance.
Transverse Beam Profile
Size (rms): 2.0-5.0 mm. 5% (LP) 20 μm (LP) Required in the low power (LP) only. In the high power regime (HP), position will be sufficient.
Beam Halo, measure/remove
Full aperture 20%1 nA, assuming
2π scraperWorking in the low and high-power regime. A factor of 100 better accuracy is required for RHIC II R&D.
AP requirements (Low Energy 2.5 MeV Injection Transport / Dump)
E. Pozdeyev 4-15
Optical Transition Radiation
Maximum intensity at angle /1
“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
Use metal coated silicon wafer screens (V.L.)
0 5 10 15 200
0.005
0.01
0.015
0.02
0.025
0.03
E (MeV)
Eph
(e
V),
QE
energy per electron (eV)effective QE
0 5 10 15 2010
2
103
104
105
E (MeV)N
ph/(
10
m x
10
m)
1 nC/mm2
0.1 nC/mm2
Energy radiated by an electron and effective QE
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.
Depending on energy,light collection efficiency can be of the order of from <0.01 for low E to >0.3 at high E.
OTR Efficiency
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
nCmm
nCS
dS
dQq 13.02.02.01
2
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.
Typical CCD:Noise floor 10 ph-e-/pixelCan see 100-1000 ph-e-/pixel
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 thick3.5MeV, 2us pulsed beam
A. Warner, Fermi, 2005
YAG crystal considerationspC 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
nCm
CS
dS
dQq
sat
22002001022
14
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.)
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
ERL Injection Layout
Flag 1
Flag 2
ERL Extraction/Dump transport
?
Flag 3
ERL Loop Layout
Dump Flag
Flag 4
Flag 3
Flag 2Flag 1
Flag 5
Wire Scanner
ERL Loop Vacuum Crosses2 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
Radiabeam IBISRadiabeam 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 axisStandard Radiabeam IBIS Profile Monitor
Dual purposeThree position Plunger head
Impedance Matching
Full retract position “squirrel cage”Not perfect:
Cross geometryVacuum conductance
Slots in cage, need size details:beam perspectivevacuum perspective
Daresbury Solution
Actuator Detail &Viewing port
Need external survey fiducials on actuator housingSurvey can locate to 100um accuracy.
Radiabeam YAG Screen Profile MonitorBeam direction
LensCamera
filt
erYAG Screen
Optics Box
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)
Radiabeam Optics Box
Radiabeam IBIS resolution:“Better than 20um”
ERL ModificationsSpecify CameraReplace 3-motion lens:
zoomfocusiris
With fixed lens & ND Filter wheel
Calibration:OTR Fiducialized screenYAG Fiducialized maskRadiabeam will provide a simple alignment fixture to ensure decent mechanical to start. Need insitu alignment scheme? Rotatable flangesSurvey fiducials on actuator body
Better than 1 degree accuracy
YAG, OTR & Synchrotron Light DAQ
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)
Use Unibrain FireRepeater 400To get camera data to 1394 Interface
Alternative DAQ:Mindready Sednet 1394, used at Diamond
- Dedicated image processing computer- Ethernet bandwidth is low
-Image processing done on microIOC server
Cosylab CosyEye microIOC tech-spec
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
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