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