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.