Conclusion and Outlook (2)

� OTR (the working horse) will not be as easy to use as it used to be

need to mitigate COTR (experimental demonstration)

� At the present light sources there is a lot of experience with SR diagnostics

for non distracting beam measurements. A lot of that can be applied to ERLs

with emittance ~ 10 times better.

� Beam loss and synchronization (see talk by Florian and Lars)

Other important issues to discuss at the workshop and talk on Friday

will the COTR mitigation work for ERL parameters?� will the COTR mitigation work for ERL parameters?

� for light sources: beam stability, orbit feedbacks – extend experience of 3rd

generation light sources and large scale LINACS

� CW beam monitoring

� Optical Diffraction Radiation (ODR) applicability

� Transfer function (transverse and longitudinal) measurements and monitoring

ERL Instrumentation Discussions

• Diagnostics of high current CW beams especially at low energies in the injector region

is an area where we have least of experience:

- mostly beam profile measurements

- BPMs for beam position work

- bunch length (longitudinal profile)

• At high energy outside of the LINAC can used SR the same way at the presently operated

high energy rings

- the BIG difference is that LINAC beams are not Gaussians, since they are not in

equilibriumequilibrium

- pin hole cameras

- zone optics systems

- two slit interferometer with visible SR

• Can not do that in the LINAC

- Can ODR be used?

- main question is if the presence of the radiator close to the beam will be acceptable

- Laser wire

• Make use of the fact that the beam is CW – very small modulation + lock-in amp

Flying wire

• 20 m/s flying carbon

wire

• Applicable with 0.6

MW of beam power

• Two units, one in

dispersive section to

allow studies of long-

April 20, 2010 I.V. Bazarov, Flying wire at Cornell University

allow studies of long-

range wake fields

Flying wire

April 20, 2010 I.V. Bazarov, Flying wire at Cornell University

signal from a laser test

• Installed on the injector beamline

• Ready to be tested with beam

test headline

Laser-wire R&D: Intro, results from PETRA II and SNS

• Main focus of R&D studies was to build non-destructive beam profile monitor for ILC-like beams (up to 250 GeV beam energy, several nC bunch charge)

• For beam sizes– in the μm range in the beam delivery systems– down to nm spots at the interaction point

• At low beam energies (< 50 MeV) not yet succesful tested. Opening angle of Compton scatted photons large

T. Kamps

test headline

PETRA 2D laser-wire: experimental setup to study laser-wire issues for ILC beams

• Use injection seeded Q-switched Nd:YAG laserwith several MW peak power and ns pulse length

• Achieved 2D scans of several 10 μm spot sizes several 10 μm spot sizes within 50 sec measurement time

• Consider faster scans with kHz laser and ps pulses

• Original goal is to achieve full profile measurement within one bunch train of the ILC

Courtesy G. Blair, S. Boogert, NIM A 592 (2008)

T. Kamps

test headline

Laser-wire at SNS

• Laser-wire photo-neutralizes the H- beam from the SNS linac• Stripped-off electrons flux is measured for each laser position in

bending magnet with electron detector• One Q-switch laser serves 9 laser-wire stations• Measure profiles within one bunch train of 650 ns length

Courtesy T. Shea, Y. Liu, Assad, Proc. of HIB 2008, EPAC 2008 T. Kamps

Potential nonPotential non--destructive profiledestructive profile

monitors for the Cornell ERLmonitors for the Cornell ERL

Non Destructive Profile Monitors F.Sannibale

•• Pinhole xPinhole x--ray cameraray camera

•• Fresnel optics systemsFresnel optics systems

•• Optical synchrotron radiation 2Optical synchrotron radiation 2--slit interferometerslit interferometer

8

Instrumentation Workshop for ERL @ CSR, Ithaca, NY USA, June 2, 2008

•• Laser wiresLaser wires

•• OthersOthers

LINAC beams are different from ring beams

JLab FEL transversal beam profile:

• Obtained in a specially setup measurements to show how much beam is non Gaussian

• It in not how we have it during standard operation

• There is no Halo shown in this measurements in sense that all of it participates in FEL

interaction

• The techniques we can borrow from rings assume Gaussian beam and therefore

are concentrating on beam size (RMS) measurements �

Optical Diffraction Radiation

)(10 rK

v

qEr ⋅

⋅

⋅= α

π

αω βγλ

πα

⋅⋅

⋅=

2

amplitude of a Fourier componentof transversal Coulomb field of anelectron

),( yxfb - transverse beam distribution

intensity of the ODR from the beam

unpolarized

vertically polarized

horizontally polarized∫∫ ⋅⋅−−⋅=

beam

rbbeam ddyxEfI ψξψξλγψξπ

ω2)],,,([),(

8

1

intensity of the ODR from the beamIs 2D convolution of the fb and Erω

2

Example assuming

4.597 GeV;

σx=215 µm; σy=110 µm;

λ=550 nm; h=1.1 mm

5µµµµA tune beam; OTR

10µµµµA CW beam; ODR V. polarized

Fig. 1

Fig. 3Fig. 4

Fig. 5

Diagnostics

and and

Machine Protection from WG2

X-Band Cavity BPM Designed for LCLS (R. Lill, ANL)

� Each BPM has Dipole and Monopole cavity for

measuring position and beam intensity

� Design strengths

– Sub-micron resolution

– Inherent centering accuracy and reproducibility

– Very successful in LCLS commissioning

� Challenges for ERL

– Fast response for machine protection– Fast response for machine protection

– Multiple beams in linac

– High dynamic range needed for ramp-up

– Complex installation and need for z space

X-ray BPM Development: Pinhole Camera XBPM (B. Yang, ANL)

� Pinhole camera used as an x-ray beam position monitor

� Transverse resolution ~ 30 nm with 0.1 Hz filter

� Observed horizontal beam motion: 300 nm @ 1-minute interval

� Observed vertical beam motion:

1 µm peak-peak related with

0.1 deg water temperature change

Diagnostics @ ALICE

Susan Smith Daresbury

Quick review diag

ALICE to EMMA TL

EO, beam arrival, timing and synchronisation

EMMA BPMs

EO, beam arrival, timing and synchronisation

Collimation and Tomography Systems for NLS (D. Angal-

Kalinin, ASTeC)

• Collimation needs : Machine protection, Undulator demagnetisation,

photoinjector

3rd harmonic cavity

BC1 BC2 BC3

laser heater

accelerating modules

collimation

diagnostics

spreader

FELs

IR/THz undulators

gas filters

experimental stations

• Collimation needs : Machine protection, Undulator demagnetisation, radiation levels

• Collimation immediately after the gun and considerations for the post Linac collimation

• Simple post Linac collimation system need ~40m of length and thus a collimation system is foreseen to be before the beam switchyard

• Collimation wakefields and emittance degradation can be important

• Tools and experience available from linear collider

• 6D Tomography section proposed to be included in additional branch of the switchyard to mimic the effect of switchyard

Discussion Points and Comments

• Cost of cavity BPMs was a concern (20k$/channel), but can

be reduced with design improvements

– Could use for undulator locations only

• Must think carefully about how to implement cavity BPM

with CW beam at high rep rate

– Any beam impedance issues?

– Should try such a BPM on existing ERL

• X-ray pinhole is sensitive to position, whereas in light

sources we need to control angle as well

– Can be paired with more standard x-ray BPM

� Method for halo detection: coronagraph (high energy) / ? (low

energy)

� Beam-loss monitors for human/machine protection:

� Need to install them close to beams

� How fast can they be without being unreliable? (A few-µs response is

desirable)

Collimation at low-energy (e.g., in merger)

Discussion: Diagnostics and Machine Protection

� Collimation at low-energy (e.g., in merger)

� Does the collimator degrade the beam quality?

� Halo prevention is better than collimation.

• How to protect SC-cavities from beam impact?

� How to distinguish x-rays from cavity from beam losses near cavity?

� Start-up process including verification of beam orbit will be necessary.