# Presentation: 749642

## 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?

## 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 ppm | Working 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, norm | Pepper 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 scraper | Working 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

- “The OTR screen is a better choice when a beam intensity integrated over a CCD frame (33ms) duration exceeds 1 nC/mm**2”**.
- 	Alex Murokh - Radiabeam

**Use metal coated silicon wafer screens (V.L.)**

## OTR Efficiency

- 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.

- 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.

- _Typical CCD:_
- Noise floor 10 ph-e-/pixel
- Can see 100-1000 ph-e-/pixel

## YAG:Ce Screens

-  Dynamic Range
- YAG:Ce scintillator is a better choice under 0.1 nC/mm**2**
-  Beam profiles & position at low intensities: **1nA – 1****μ****A (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_[ ](http://images.google.com/imgres?imgurl=http://www.starizona.com/ccd/advimages/ccdqe.jpg&imgrefurl=http://www.starizona.com/ccd/procadvcolor.htm&h=294&w=382&sz=18&hl=en&start=63&tbnid=dFlIzGyhZxQ0IM:&tbnh=95&tbnw=123&prev=/images%3Fq%3D550nm%26start%3D60%26ndsp%3D20%26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DN)_(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

## 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.)

## 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 2

- Flag 1

- Flag 5

- Wire
- Scanner

## 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

## 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

## Dual purposeThree position Plunger head

- Dual purposeThree position Plunger head

## 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**

## Actuator Detail &Viewing port

- Actuator Detail &Viewing port

- Need external survey fiducials on actuator housing
- Survey can locate to 100um accuracy.

## Radiabeam YAG Screen Profile Monitor

- Beam direction

- Lens

- Camera

- filter

- YAG 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 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**

## YAG, OTR & Synchrotron Light DAQ

- _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 400
- To 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

- _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