DEVELOPMENT OF A BEAM DEVELOPMENT OF A BEAM LOSS DETECTION SYSTEM FOR LOSS DETECTION SYSTEM FOR
THE CLIC TEST FACILITY 3THE CLIC TEST FACILITY 3
T. Lefevre
• Beam loss monitors for the CLIC Test Facility 3
• Preliminary study done in 2003• Geant3 simulations• First experimental data
• Conclusions & Perspectives
BIW 2004, 5 May 2004
T. Lefevre, M. Velasco , M. Wood, Northwestern University
H. Braun, R. Corsini, M. Gasior, F. Tecker, CERN
T. Lefevre BIW 2004, 5 May 2004
CLIC Test Facility 3CLIC Test Facility 3
• The CLIC Test Facility 3 is built to demonstrate the Compact LInear Collider The CLIC Test Facility 3 is built to demonstrate the Compact LInear Collider feasibilityfeasibility
- Drive Beam Generation :
- Efficient way of producing a high current (35A) high frequency (15GHz) 150MeV and 1.6s electron beam
- Done using a fully loaded linear accelerator (94% RF to beam efficiency) and two rings
- Drive Beam Deceleration stability (two beam acceleration section)
- The beam is strongly decelerated in order to provide the 30GHz RF source
- Study the Beam halo & Beam loss mechanisms
- Provide a 30GHz power source to continue the R&D program on high gradient accelerating structures (150MV/m)
- Housed in the LEP injector complex and scheduled for completion before 2010.
- The construction of the linac will be finished by the end of the year
BLM for CTF3 Linac BLM for CTF3 Linac
T. Lefevre
• Northwestern University joined the CTF3 collaboration in 2003 and we are designing and building the beam loss detection system for the CTF3 linac.
BIW 2004, 5 May 2004
• The operation of a fully loaded linear accelerator
• Heavy beam loading in accelerating structures Transient effects where the energy gain per cavity for the beam head can be twice higher than its nominal steady state value
• Beam transient compensation scheme by adjusting the delay between the beam and the RF signal in the cavities
• We designed our system to observe the beam transient loss
• Dangerous beam losses : > 10% of the total beam charge (6C)
• The protection system will rely on wall current monitor
• The BLM system will be a tool for the optimization of the Linac operation
T. Lefevre
Beam position monitor
Acceleratingstructure
Quadrupoles
e-
Beam loss detectors• Fast time response (ns-10ns) for beam transient study• Segmented X-Y beam loss positioning for tuning
Yz
x
Typical Linac section
Design beam optics
High probability that beam loss occurs in the quadrupole region
BIW 2004, 5 May 2004
Goal : To install the BLM at a position where the beam transient would be lost
BLM for CTF3 Linac BLM for CTF3 Linac
T. Lefevre
Beam pipe simulations : Transverse distribution of the e-/e+ shower
Geant3 SimulationsGeant3 Simulations
100MeV
• The total flux of electrons in the shower is proportional to the electron energy• With higher beam energies, the shower asymmetry is more pronounced
BIW 2004, 5 May 2004
Simulations based on a beam loss corresponding to the ‰ of the nominal beam current e-
Position of observation : 1m dowstream Beam loss
at + Y
T. Lefevre
Beam loss in the Central quadrupole
Geant3 SimulationsGeant3 Simulations
BIW 2004, 5 May 2004
Beam loss Positions of observation
e-
Screening effect of the 3rd quadrupole which
reverses the transverse distribution of the e-/e+ Shower
Z=25cm Z=75cm Z=120cm Z=155cm
T. Lefevre
done by Matthew Wood
Positions of the beam loss
ee-- shower efficiency shower efficiency : Number of particles detected / Number of particles lost
Geant3 SimulationsGeant3 Simulations
BIW 2004, 5 May 2004
e-
BLM’s(size and position)
•35MeV, 0mm beam size, 3mrad beam angle• Beam loss at + Y• Ø40mm detector installed at 15cm from the beam axis
Simulations
• The shower transverse distribution is affected by the presence of Quadrupoles• For losses on the beam pipe the asymmetry corresponds to 50%• Beam loss position more than 2 orders of magnitude difference in the shower efficiency • For losses > 1‰ of beam current Detector must be able to measure currents > 100nA
+ Y+/- X- Y
T. Lefevre
Test on CTF3 in 2003 Test on CTF3 in 2003
Using the collimator in the cleaning chicane to study the beam transient
BIW 2004, 5 May 2004
Collimator
BPM502
BPM690Accelerating structures
BPM402
Quadrupoles
e -
Beam line layoutBeam line layoutDipoles
Injector
Two Aluminum Cathode Electron MultipliersØ40mm, Sensitivity range [100nA-100mA]
Beam loss
monitors
Cleaning chicane
Steerers
First Linac Section
T. Lefevre
0 200 400 600
-3
-2
-1
0
Slit aperture 14 Slit aperture 19 Slit aperture 23 Slit aperture 27
BPM
502
curr
ent
(A)
t (ns)0 200 400 600
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
Slit aperture 14mm Slit aperture 19mm Slit aperture 23mm Slit aperture 27mm
Beam
loss
cur
rent
(mA)
t (ns)
Observation of the beam transient loss Observation of the beam transient loss
Chicane &Collimator
Case 1 : Slit opened
< 80MeV 35MeV
•The slit is opened so that the full beam enters the next accelerating structure.
•The beam transient is then re-accelerated up to 80MeV and is lost somewhere because the beam optics are not adapted to its energy
BIW 2004, 5 May 2004
Case 2 : Slit Closed
< 35MeV
20MeV
•The slit is closed so that the beam transient is stopped in the collimator.
•The rest of the beam enters the next accelerating structure and is accelerated to 35MeV
0 200 400 600 800-5
-4
-3
-2
-1
0 BLM Right BLM Left
BLM
cur
rent
(mA)
t (ns)
0 200 400 600 800-10
-8
-6
-4
-2
0 BLM Right BLM Left
BLM
cur
rent
(mA)
t (ns)
T. Lefevre
Slit closed : Horizontal and Vertical scansSlit closed : Horizontal and Vertical scans
BLMLeft
BLMRight
e-
0 200 400 600 800-5
-4
-3
-2
-1
0 BLM Right BLM Left
BLM
cur
rent
(mA)
t (ns)
0 200 400 600 800
-6
-3
0 BLM Right BLM Left
BLM
cur
rent
(mA)
t (ns)
Beam goes to the Left Beam goes to the Right
Beam goes Down
Beam goes Up
•In vertical scans the beam loss is equally distributed on the two detectors and their output signals are equivalent (<5% difference)
•In horizontal scans the BLM output signals are different in a ratio of 2 (40-60%)
Localizing the beam loss transversely ?
BIW 2004, 5 May 2004
Geant3 expectationsGeant3 expectations
T. Lefevre
ee-- shower efficiency for different shower efficiency for different beam loss positions and energiesbeam loss positions and energies
Beam loss position 1st Quad 2nd Quad
3rd Quad Pipe 0.9m
Pipe 0.3m
Shower efficiency (%)
5.25 10-
4
1.4 10-3 9.3 10-3 2.7 10-2 0.2
35MeV, 3mrad, 0mm beam size
80MeV, 3mrad, 0mm beam size
Beam loss position 1st Quad 2nd Quad
3rd Quad Pipe 0.9m
Pipe 0.3m
Shower efficiency (%)
4.6 10-3 8.9 10-3 4.5 10-2 9.9 10-2 0.28
BIW 2004, 5 May 2004
-2 -1 0 10.04
0.06
0.08
0.10
-2 -1 0 10.0
0.2
0.4
0.6
0.8
1.0
1.2
Transient
BLM
/BPM
cur
rent
(%)
Steerer current (A)
Steady state
T. Lefevre
Vertical scan with the slit opened
0 200 400 600 800-1.5
-1.0
-0.5
0.0
BLM
cur
rent
(mA)
t (ns)
0 200 400 600 800
-1.2
-0.8
-0.4
0.0
Beam centered I=0.5A I=-1A I=-1.7A
Beam
cur
rent
lost
mea
sure
d us
ing
BPM
(A)
Close to the detector
Detector 3rd Quad
3rd Quad
3rd 2nd Quad
35 < E < 80MeV
E = 35MeV
1. Using BPM data’s to estimate the beam current lost in a linac section2. Using the BLM measurement to estimate the Z position of the beam
loss
BIW 2004, 5 May 2004
T. Lefevre
ConclusionsConclusions
• Beam loss transverse positioning works in agreement with the Geant3 predictions
• During this test, the beam losses were relatively high (beam transient ~ 1A) and they were located near the quad’s region (which was consistent with the design lattice)
• Using the BPM’s data & the energy measurements, the BLM system can be used to localize the losses along the accelerator accurately (< 50cm)
• Without the BPM data, one system per section is not enough to monitor beam loss intensity & position (more complicated for beam losses distributed along the linac)
How can we be quantitative : I & Z ?
• Adding detectors every 50cm to get the Z beam loss position:
• Longitudinal positioning using a Cherenkov fiber and a time of flight measurement (already developed at SLAC and TTF)
BIW 2004, 5 May 2004
T. Lefevre
Perspectives Perspectives
BIW 2004, 5 May 2004
• The system to be installed in the next months :
• The detectors are developed at Northwestern University (M. Velasco and A. Dabrowski) in conjunction with Fermilab (G. Tassotto)
• 12 sets of 4 detectors (SEM/SIC) located near the quadrupoles region
• Special set-up to study the losses one a single linac section using 12 detectors
• The signals are then amplified and acquired using 100MHz ADC’s
1mm gap chamber
• Can be operated with gas (ionization) or vacuum (SEM) • Radiation hard
T. Lefevre
CTF3 little shop of horrors CTF3 little shop of horrors
BIW 2004, 5 May 2004
Damage on a Vacuum valve
Spectrometer line
Respect
the steering limitation
T. Lefevre
Suggestion !Suggestion !
BIW 2004, 5 May 2004
The CLIC Test Facility 3The CLIC Test Facility 3
T. Lefevre
Drive Beam generation : Efficient way of producing a 35A beam bunched at 15GHz• Acceleration of a high current beam in a 3GHz fully loaded Linac (95% RF to beam efficiency)
• Production of a high frequency (15GHz) bunched beam using a delay loop and a combiner ring
CLEX : CLic EXperimental area: • Provide a 30GHz power source for the development of high gradient (150MV/m) accelerating structures
• Test the Drive beam stability in the Drive Beam Decelerator (beam loss rate)
• Housed in the LEPPre-injector complex
• Scheduled for completion before 2010
BIW 2004, 5 May 2004
30 GHz Power Source and distribution line
3TeV Compact LInear 3TeV Compact LInear ColliderCollider
T. Lefevre
e- Main Linac e+ Main LinacBDS
Damping rings• 4ps, >10me-/e+ Source
• 42ns, 2,424GeV• 157 bunches (400pC)• 4ps, >50m
Main Linac• 9 1500GeV• 100fs, >1m
CombinerRing 1
Delay loop
CombinerRing 2
Source
25 Drive Beams Decelerators per linac• 1.79GeV, 144A over 56ns• 1ps, >50m
Drive Beam Generator •4.5A over 92s with an final energy of 1.79GeV: 43000 bunches (9.6nC each)• 10ps, >50m
BIW 2004, 5 May 2004
What have been achieved up to What have been achieved up to nownow
CTF3 – Preliminary phase - 2002Low-charge demonstration of electron pulse combination and bunch frequency multiplication by up to a factor 5
Streak camera image of the beam
time structure evolution
LEP injector EPA ring
Operation of a fully loaded linacOperation of a fully loaded linac
T. Lefevre
Drive beam acceleration in 2003
Beam current – BPM 402
4 A
1.5 s
Beam current 4 ABeam pulse length 1.5 sPower input/structure 35 MWOhmic losses (beam on) 1.6 MWRF power to load (beam on) 0.4 MWRF-to-beam efficiency ~ 94%Phase variation along pulse ±4º
RF signals / output coupler of an accelerating cavity
RF phase
RFpower Power to load (beam
off)
phase
Power to load (beam on)
±4º
1.5 s
Heavy beam loading in the accelerating structure
Beam head sees a much higher accelerating field
Strong transient effects so that in the first 50ns of the pulse the beam energy can be twice higher than the energy of the rest of
the beam
Beam transient compensation by adjusting the delaying the RF pulse in the
accelerating structure to suppress the transient effect
BIW 2004, 5 May 2004
BLM detectorsBLM detectors
T. Lefevre
Two different types of detectors (ns time response) have been tested in parallel
- A 4mm thick plastic scintillator (Ø40mm) coupled to XP2020 photomultiplier tube
e-/e+VisiblePhotons
1.75%
e-
Photocathode25% QE • e- / e+ :
[1, 20]MeV 500 - 1000 photo-e-
• & x rays : [10keV,20MeV] 4 - 100 photo-e-
e- current amplification<106- 107
HV
Scintillator
Signal
x &
rays 50mV/50Ω A-pA
- An Aluminum Cathode Electron Multiplier (ACEM) (Ø38mm)
e-/e+
x &
rays
Aluminum cathode100nm thick • e- / e+ :
[1, 20]MeV 1 - 5% SEM e-
• & x rays : [10keV,20MeV] 4.10-6- 2.10-9 SEM e-
e- current amplification<105- 106
e- HV
Signal50mV/50Ω 100mA-100nA
BIW 2004, 5 May 2004
1.5 1.6 1.7 1.8 1.9 2.01E-4
1E-3
0.01
0.1
1
0.32V
Sin
gle
phot
on s
igna
l (m
V)
PMT High Voltage (kV)
For 1.5kV High voltage
20keV energy deposition 0.32±0.03V
1mV 6.2±0.6MeV
(≈ the calibration using radioactive sources)
Calibration is done at ESRF using a 20keV X-ray beam
BLM detectors : BLM detectors : CalibrationCalibration
0.4 0.6 0.8 1.0
1E-12
1E-11
1E-10
1E-9
1E-8
1E-7
5.8pA
14pA40pA
Calibration using a 330MBq 137Cs Source
I (A
)
High voltage (kV)
Calibration using a very intense Cesium source
( - emitter: 53pA)
High Voltage (V) 500 400 300
ACEM current (pA) 40 14 5.8
Efficiency (%) 75 26 11
Output voltage on 50Ω (nV)
2 0.7 0.3
Calibration : 1mV xx A
26.5 75.7 177
ACEMScintillator + PMT
T. Lefevre BIW 2004, 5 May 2004
Lattice design in a linac sectionLattice design in a linac section
Example in the central Quad:
≈ 10m ≈ 100 .mm.mrad≈ 80 (40MeV)
≈ 6mm
)().(
)(mmmradmm
mm
Beam size
Beam emittance Relativistic factorBPM790
BPM890
Quadrupoles
Steerer
Beam lossdetectors
T. Lefevre BIW 2004, 5 May 2004
Beam optics reconstructed from experimental dataBeam optics reconstructed from experimental data
T. Lefevre
BLM’s
• High probability to have beam losses in the quadrupoles region
BIW 2004, 5 May 2004
35MeV, 0mm beam size
T. Lefevre
done by Matthew Wood
• Beam loss position more than 2 orders of magnitude difference in the shower efficiency
• Can the longitudinal beam loss position be determined by the ‘angular shower shape’ ?
80MeV, 0mm beam size
Positions of the beam lossShower asymmetry as a function of the beam loss position
Geant3 SimulationsGeant3 Simulations
BIW 2004, 5 May 2004
T. Lefevre
done by Matthew Wood
Shower versus beam angle
• During this test we were using very small steering forces (I<1.5A) so that 5mrad can be considered as a maximum deviation angle
• Beam loss angle effects are small compared to the effect due to the beam loss position
35MeV
Positions of the beam loss
Geant3 SimulationsGeant3 Simulations
BIW 2004, 5 May 2004
T. Lefevre
done by Matthew Wood
~ e-/ e+ shower of 0.3nA, not seen by the ACEM with a 400volts bias
Shower generated by the beam losses in the collimator
Geant3 SimulationsGeant3 Simulations
BIW 2004, 5 May 2004
T. Lefevre
Example 1Example 1 : Observation of the beam transient loss : Observation of the beam transient loss
• Time – Energy correlation in the beam transient (Each slit aperture selected a given beam energy range between 35-70MeV)
• You normalize the BLM signals to the beam current loss seen by the BPM502 (≈ BPM690)
16 18 20 22 24 26 28
0.05
0.10
0.15
0.20
0.25
BLM
/BPM
cur
rent
(%)
Slit aperture (mm)
‘BLM signals depend on beam energy, position and current’
Possibility to estimate where the beam transient is lost
• The different energies are not lost at the same position
• Beam loss distributed between the detector and the 3rd quadrupole
Low - - - - - - - - - high energy
BIW 2004, 5 May 2004
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