Post on 13-Jan-2016
description
f
Optical Transition Radiation (OTR) Detectors for Beam Diagnostics
Vic ScarpineInstrumentation Department
Accelerator Division
Jan. 17, 2006
Jan, 17, 2006 Accelerator Physics & Technology Seminar
2
f Outline
This is a general survey talk on OTR detectors for beam diagnostics
1. Introduction• What is OTR and why is it useful for beam diagnostics?
2. OTR detectors at other accelerators
3. OTR detectors at Fermilab• E-cool, A0, p/pbar transfer lines, Tevatron, Numi
4. Future applications of OTR for beamline diagnostics
Jan, 17, 2006 Accelerator Physics & Technology Seminar
3
f Introduction
What is Optical Transition Radiation?Optical Transition Radiation (OTR) is generated when a
charged-particle beam transits the interface of two media with different dielectric constants, for example, vacuum to metal
OTR detectors have been used with high energy and intensity electron beams
CERN has tested OTR detection with proton beams and are using them extensively
– Initial proton experiment at CERN-SPS in 1984
Jan, 17, 2006 Accelerator Physics & Technology Seminar
4
f OTR Emission Patterns
2222
22
2
21
2
)(
)(1
yx
yx
hc
e
dd
Nd
Quantity of light proportional to foil reflectivity for reverse OTR
Emission spectrum is very broad – signal in visible region
Protons
o
Normal Incidence
Protons
o
Oblique Incidence
Jan, 17, 2006 Accelerator Physics & Technology Seminar
5
f OTR Intensity Profile
Jan, 17, 2006 Accelerator Physics & Technology Seminar
6
f Ray Diagram for OTR Imaging
Jan, 17, 2006 Accelerator Physics & Technology Seminar
7
f OTR Detector Strategy
• Convert particle beam information to optical radiation and then use COT imaging technology to acquire beam information
• Use thin foil to minimize beam scattering• Beam image provides 2-D information on:
– Transverse profile and shape (tilt)– Transverse position– Emittance– Intensity– Divergence, energy, bunch length, longitudinal profile…
Jan, 17, 2006 Accelerator Physics & Technology Seminar
8
f OTR Detectors for Beam Diagnostics
• OTR detectors are a primary beam diagnostics tool at many accelerators – mostly electron machines
• Quick search of JACoW (Joint Accelerator Conference Website) for titles with “optical transition radiation” produces 173 papers.
• OTR detectors used at:– Argonne APS, Los Alamos FEL, Jefferson Lab, Beijing FEL,
BESSY FEL, Final Focus Test Beam at SLAC, Tesla Test Facility, ELETTRA Linac, Linac Coherent Light Source FEL, Fermilab, CERN SPS, etc
– To numerous to discuss them all…
Jan, 17, 2006 Accelerator Physics & Technology Seminar
9
f First OTR Detection for Electron Beams (1975)
40-60 MeV electrons
Jan, 17, 2006 Accelerator Physics & Technology Seminar
10
f Two-Foil Interferometry
Two-foil interferometry for electron beams to measure energy and beam divergence
– Energy from positions of interference peaks
– Divergence from modulation of interference pattern
Jan, 17, 2006 Accelerator Physics & Technology Seminar
11
f Two-Foil Interferometry
Jan, 17, 2006 Accelerator Physics & Technology Seminar
12
f High Power Beam Profile OTR Monitor at CEBAF
• High power beam – 800 kW
• 0.8 to 4 GeV electron energy
• Forward OTR from 0.25 carbon foil– Independent of reflectivity of C
• Small beam size ~ 100
Jan, 17, 2006 Accelerator Physics & Technology Seminar
13
f OTR Emission for Small Beams
• Issue of measuring the small beam profiles – what is limiting resolution?
– Is there a uncertainty in OTR photon emission position?
– This detector measures 100 rms size of a 3.2 GeV beam - is 3.2 mm
• Standard optical diffraction seems to limit OTR resolution up to very
high
f
OTR Detectors at Fermilab
Jan, 17, 2006 Accelerator Physics & Technology Seminar
15
f OTR Detectors for E-cool
• OTR monitors are being used with pulsed beam to image and model the charge distributions of the 4.3 MeV electron beam used in the electron cooler at Fermilab.
– A. Warner, A. Burov, K. Carlson, G. Kazakevich, S. Nagaitsev, L.Prost, M. Sutherland, and M. Tiunov
• Highly-reflective 2 inch-diameter 5 µm aluminum OTR-screen
• The measurements are done in a pulse-signal mode in the beam current range of 0.03-0.8 A and at pulse durations ranging from 1 µs to 4 µs.
Jan, 17, 2006 Accelerator Physics & Technology Seminar
16
f E-cool OTR Linearity
• The dependence of the integral of detected light in the beam spot versus the beam current
• Shows good linearity of the OTR monitor.
0 100 200 300 400 500 600 7000
20
40
60
80
100
120
140
Inte
gra
l, re
l. un
its
I beam, mA
Jan, 17, 2006 Accelerator Physics & Technology Seminar
17
f E-cool OTR Profile Measurements
300 400 5000
5
10
15
20
25
30
ISPA06
=22 A
ISPA06
=14 A
ISPA06
=6 A
Up=4.5 kV; 2 s-1 s;Scale: 15.93 pix/mm
Inte
nsity
, rel
. uni
ts
Y, pix.
300 400 500 600 7000
5
10
15
20
25
30
ISPA06
=22 A
ISPA06
=14 A
ISPA06
=6 A
Up=4.5 kV; 2 s-1 s; Scale: 19.74 pix/mm
Inte
nsi
ty, r
el.
units
X, pix.
• X and Y beam profiles versus current in lens SPA06
Jan, 17, 2006 Accelerator Physics & Technology Seminar
18
f E-cool Beam Optics Simulations
Beam profiles can not be explained as a trivial effect of focusing with SPA06 lens.
Simulations of the beam optics in DC mode from the cathode to the OTR monitor with space charge effects included.
Measured rescaled (dots) and calculated (solid lines) beam profiles for the SPA06 current values of 6 A (blue color), 14 A (red color), and 22 A (green color).
Current density distribution on TRA07 for Upulse = 4.5 kV (Ibeam = 0.56A)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
-12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12
X, mm
J, A
/cm
^2
- measurement J(x') for Ispa6=6A
- measurement J(y') for Ispa6=6A
- measurement J(x') for Ispa6=14A
- measurement J(y') for Ispa6=14A
- measurement J(x') for Ispa6=22A
- measurement J(y') for Ispa6=22A
- BEAM calculations for Ispa6=6A
- BEAM calculations for Ispa6=14A
- BEAM calculations for Ispa6=22A
Jan, 17, 2006 Accelerator Physics & Technology Seminar
19
f OTR Detectors at A0
Jan, 17, 2006 Accelerator Physics & Technology Seminar
20
f Plasma Focusing of Electron Beam
Jan, 17, 2006 Accelerator Physics & Technology Seminar
21
f OTR Interferometry at A0
Working being done by Gregory Kazakevitch to measure beam energy
I and II are OTR screens.The electron passing through OTR I radiates due to interaction with the screen II the photon-II, which interferes with the photon-I reflected from screen II.
The phase shift one can express as:
)sin(coscos1sincos
sin
cos
1
cos
1221
e
dkn
Here 1 and 2 phases of the photon-I and photon-II respectively.
Jan, 17, 2006 Accelerator Physics & Technology Seminar
22
f Interference Patterns
Calculated interference patterns for = 30 and = 30.5 electron beams
0.05 0.04 0.03 0.02 0.01 0 0.01 0.02 0.03 0.04 0.050
1000
2000
3000
40003.112 10
3
0
U 1 ( )
U 2 ( )
0.050.05
The interference method allows to separate the difference in the energy of the electrons and also is applicable to the emittance measurements.
f
OTR Detectors at Fermilab for Proton and Antiproton Beams
Jan, 17, 2006 Accelerator Physics & Technology Seminar
24
f OTR Detectors for Fermilab Proton and Antiproton Beams
• Will OTR detectors work for Fermilab transfer lines?
• Compare to electron machines to determine feasibility for FNAL
Jan, 17, 2006 Accelerator Physics & Technology Seminar
25
f Prototype OTR Location – AP1 Line
• Fairly frequent access to location
• Location immediately available
• Frequent beam- stacking• High intensity – 4e12• High energy – 120 GeV
– 1/ -> 8 milliradians
• Beam size of 1 ~ 1 mm• High radiation environment?
~ 6 krad/wk at 1 meter
Jan, 17, 2006 Accelerator Physics & Technology Seminar
26
f Prototype OTR Block Diagram
CIDcamera
Calib Light
UpstreamDownstream
CableInterface
Box
Pre-VaultEnclosure
F23 ServiceBuilding
CameraController
Motion Control&
Lighting
377TriggerModule
Frame Grabber
A to D/D to A
VideoMonitor
AP-1 Line
PC
LVDT
Jan, 17, 2006 Accelerator Physics & Technology Seminar
27
f Prototype OTR Block Diagram
Jan, 17, 2006 Accelerator Physics & Technology Seminar
28
f Images with 12 Titanium Foil
• Proton intensity ~4.5e12• Using x0.005 light attenuator• Measurements down to ~ 5e9
possible for same beam size and same
Jan, 17, 2006 Accelerator Physics & Technology Seminar
29
f Change Beam Size
Vertical beam size reduced by x2 and tracked by OTR detector
Jan, 17, 2006 Accelerator Physics & Technology Seminar
30
f OTR with 20 Aluminum Foil
• ~4.7e12 protons
• x0.001 light attenuation
• Image show some structure but need to determine if it beam or foil induced
Jan, 17, 2006 Accelerator Physics & Technology Seminar
31
f An OTR Detector for Fermilab Proton and Antoproton Beamlines
• Develop an OTR detector as part of the Run II upgrade program and as part of the NuMI primary beam line - design for high (> ~100)
Jan, 17, 2006 Accelerator Physics & Technology Seminar
32
f OTR Detectors for A150 Line
• Two OTR detectors in low dispersion region to measure emittance • Third OTR detector to measure pbar beam shape into Tevatron• Two of three OTR detectors next to multiwires
Jan, 17, 2006 Accelerator Physics & Technology Seminar
33
f Diagram of OTR detector
• Radiation hardened CID camera
• Near field/far field focusing
• Neutral density filter wheels with polarizers
• Bidirectional beam measurements with selectable foils
• Vacuum certified to few 10-9
Jan, 17, 2006 Accelerator Physics & Technology Seminar
34
f Constructed OTR Detector
• 5 mylar with 1200 angstroms Aluminum
• Back illuminated fiducials for in-situ calibration
Jan, 17, 2006 Accelerator Physics & Technology Seminar
35
f OTR Installed in Tevatron
• Installed at E0 next to new IPM• Used for single turn injection studies• Proton and pbar foils
Jan, 17, 2006 Accelerator Physics & Technology Seminar
36
f Foils Damage
The left photograph is of a 3 mil thick titanium vacuum window exposed to over 1020 120 GeV protons. The center photograph is a similar vacuum window exposed to
~3x1018 120 GeV protons but with a smaller beam spot size. The right
photograph is of our prototype OTR 20 m aluminum foil exposed to ~1019 120 GeV protons with a larger beam spot size.
Titanium has higher melting point but darkens and has more scatter
Jan, 17, 2006 Accelerator Physics & Technology Seminar
37
f OTR Detectors at CERN
• Jung, Ferioli, et al pursuing OTR detectors for many CERN transport lines:– The first (4 OTRs with 12 microns Ti and 25 microns Al/Mylar
foils) have been installed in 1998-99 to show beam profiles from PS and injected into the SPS ring at an energy of 26 GeV.
– In 2000 they installed 2 OTR (Ti foils) in the SPS ring to measure matching parameters of the circulating beam.
– In 2003 they installed 11 OTRs (Ti foils) in the extraction line of SPS and injection LHC line (TI8) to observe 450 GeV beams.
– In 2005 they are installing 7 OTRs in the CNGC line (for the Gran Sasso neutrino experiments).
– In 2006-7 they will install 5 OTRs in the TI8 beamline and ~13 OTRs in the new beamline between SPS and LHC.
– By 2007 they will have about 42 working OTRs.
Jan, 17, 2006 Accelerator Physics & Technology Seminar
38
f OTR Detectors at CERN
CERN builds their OTR detectors with many screen options
Jan, 17, 2006 Accelerator Physics & Technology Seminar
39
f Fast Profile Acquisition at CERN
• Fast OTR profiles can be acquired using fast digitizing cameras with or without MCP intensifier/shutter
• Can be used for turn-by-turn or beam time structure
• Sequence below taken with MCP gated camera at rate of 10 kHz
Jan, 17, 2006 Accelerator Physics & Technology Seminar
40
f OTR Detectors for the Future
• From ILC Diagnostic Summary for working group T9…“From the point of view of the LC design, it is clear that there are
fundamental beam size monitor performance questions that must be addressed with R&D.” Pasquinelli and Ross, 2001
“…promising new technology: 1) Optical Transition Radiation has been used to image beams below 10 m at the KEK-ATF…”
• From ILC website, Baseline Configuration Document, Instrumentation and Controls section:“Beam Profile Monitor System (Transverse)
Laserwire, etc”
Jan, 17, 2006 Accelerator Physics & Technology Seminar
41
f Optical Diffraction Radiation (ODR)
Calculated
Measured
Like OTR but using a non-intercepting target