R&D for Future Accelerators at IFIC Scientific Staff: A. Faus-Golfe, C. Alabau, J.J. García, S. Verdu, J. Alabau Technical Staff: J.V. Civera, C. Blanch

R&D for Future Accelerators at IFIC

Scientific Staff:A. Faus-Golfe, C. Alabau, J.J. García, S. Verdu, J. Alabau

Technical Staff: J.V. Civera, C. Blanch

GDE Meeting Madrid 1January 20-21

Capabilities

- CALCULATION

BEAM DYNAMICS EXPERTISE:

Electromagnetic analysis

• Electric circuits & electronics

Mechanical analysis

Optics design

Non-linear dynamics studies

New instrumentation techniques

Commissioning

3-D modelling ot BPM

Optics study for LHC non-linear collimation sysytem

- PROTOTYPING

Design: tooling, drawings

Fabrication follow-up

Assembly

Testing

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BEAM INSTRUMENTATION :

Main ongoing projects

ATF-ATF2: Beam dynamic studies and commissioning of the EXT line (LAL,KEK,SLAC)

CLIC-CTF3: BPM’s for TBL (UPC, CERN)

Pieces of BPM-TBL for CTF3


ATF and ATF2ATF was built in KEK (Japan) to create small emittance beams.

The Damping Ring of ATF has a world record of the normalized emittance of 3x10-8 m rad at 1.3 GeV.

ATF2 is being built to study the feasibility of focusing the beam into a nanometer spot (40 nm) in a future linear collider.

Extraction line drives the beam

from ATF to ATF2

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The Extraction Line (EXT)drives the beam from the ATF DR to the ATF2 Final Focus beam line

ATF and ATF2: the Extraction Line

Beam extraction process

- Shared magnets with the DR- The beam passes off-axis

Extraction Line

extractiondiagnostic section

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Hypothesis

Since several years, the vertical emittane measured in the diagnostic section of the EXT line is significantly larger than the emittance measured in the DR and present a strong dependence with the beam intensity.

The beam experiences some non-linear magnetic fields while passing off-axis through the shared magnets.

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ATF and ATF2: Emittance growth in the EXT line

ATF and ATF2: Non-linear magnetic fields in the shared magnets of the EXT line

Non-linearity of the magnetic field of the shared magnets:QM6, QM7, BS1X, BS2X, BS3X

In order to quantify the effect of the non-linearity of the magnetic field on the extracted beam, the computation of the magnetic field on

a finite mesh has been done with the code PRIAM.

Polynomial fit with the code MINUIT in order to get a continuous representation of the magnetic field:

Multipole MAD coefficients:

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Non-linearity of the magnetic field of the QM6 quadrupole

Dipole component 0.008%Quadrupole component -0.03%

Zone of interest for tracking x=0.0065m y =0m

n Kn

(m-n)

MAD notation

0 -4.6262508E-3 K0L

1 -7.1158282E-1 K1L

2 -1.2577132E-1 K2L

3 3.6353697E+2 K3L

4 1.6886595E+6 K4L

5 3.8135083E+3 K5L

6 -3.5968711+E2 K6L

7 0.0 K7L

8 0.0 K8L

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Non-linearity of the magnetic field of the QM7 quadrupole

Dipole component -2%Quadrupole component -24%

Zone of interest for tracking x=0.022 m y=0m

KN

(m-n)

MAD notation

0 8.7560676E-3 K0L

1 3.0427593E-1 K1L

2 -4.6587984E+1 K2L

3 -1.7011062E+6 K3L

4 -2.2447929E+6 K4L

5 -1.3556000E+06 K5L

6 1.9377000E+5 K6L

7 5.0501000E+4 K7L

8 2.7752000E+4 K8L

9 0.0 K9L

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Non-linearity of the magnetic field of the BS1X septum magnet

Dipole component -1.5%Quadrupole component smallSextupolar component small

Zone of interest for tracking x=0.0855m, y=0m

N KN

(m-1)

MAD notation

0 2.7619357E-2 K0L

1 7.0853673E-3 K1L

2 4.2628153E+0 K2L

3 1.8472445E+3 K3L

4 1.9177364E+5 K4L

5 -1.0264243E+9 K5L

6 -1.9285513E+12 K6L

7 -2.5274029E+15 K7L

8 -2.8330405E+18 K8L

9 -2.2953062E+21 K9L

10 -3.2264143E+23 K10LBS2X (x=0.0153m , y=0m) and BS3X (x=0.016m , y=0m) more linear part 10

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ATF and ATF2: : Tracking simulations including non-linear fields in different magnets of EXT line

Tracking performed with MAD and PLACET without horizontal bumps

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ATF and ATF2: : Tracking simulations for different x/y bump amplitudes

open the bumpin DR and EXT

offset in QM7

close the bump in the DR

Beam size after the shared magnets is correlated with the emittance:

- OTR monitor recently installed images the beam angular spread out of QM7

- Creating bumps in QM7 to probe effects on the vertical emittance

- Measure beam sizes at the DR (XSR monitor) and the EXT line (OTR monitor) as a function of the bump amplitude

OTR monitor13

ATF and ATF2: : Experimental Proposal

ATF and ATF2: Experimental Work (Dec’07-May’08)

Vertical beam size vs vertical bump amplitude at QM7

Extraction Line (OTR monitor) Damping Ring (XSR monitor)

OTR/XSR

(Measurements 19th Dec’07)14

Measurements 19th Dec 2007

Simulations:- including non-linear fields in different magnets- for different horizontal bump amplitudes in QM7 (nominal extraction 22.5 mm)- with the input emittances the corresponding to the measured during the shift

Measurements 28th May 2008

y=36 pm ~ 3*y,nom

x=2.4 nm ~ 2*x,nom

y=24.0 pm ~ 2*y,nom

x=2.28 nm ~ 1.9*x,nom

ATF and ATF2: Experimental Work (Dec’07-May’08)

σy increase at the OTR as a function of the y bump amplitude

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ATF and ATF2: Conclusions

The non-linear content of: QM6, QM7and BS1X has been calculated with PRIAM.

Tracking simulations including non-linear field errors in: QM6, QM7 and BS1X shared by both the ATF EXT line and its DR, and orbit displacements from the reference orbit in the extraction region predict a vertical emittance growth of the extracted beam.

Simulations show that the non-linear fields are very sensitive to the extraction position. The more important source on non-linearity is QM7.

Recently, measurements using closed orbit bumps in the DR to probe the relation between the extraction trajectory and the emittance growth in the EXT line have been carried out. The results shows an emittance growth with a strong dependence with the extraction position.

Both horizontal and vertical positions of the beam in the extraction region have to be controlled to avoid this emittance growth.

Based in this work QM7 will be replaced from the EXT line by a magnet with large bore to avoid the non-linear field impact.


The peak RF power required to reach the electric fields of 100 MV/m amounts to about 275 MW per active meter of accelerating structure. Not possible with klystrons.

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CLIC: The Compact Linear Collider

Each sub-system pushes the state-of-the art in accelerator design

Hence a novel power source, an innovative two-beam acceleration system, in which another beam, the drive beam, supplies energy to the main accelerating beam.

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•To demonstrate the two-beam acceleration

scheme

• A scaled facility for one branch of the Drive

Beam Generation System of CLIC

Layout of the CLIC EXperimental area (CLEX) building with TBL

CTF3: The CLIC Test Facility 3


16 TBL CellsTBL: The Test Beam Line

The main aims of the TBL:• Study and demonstrate the technical feasibility and the operability a drive beam decelerator (including beam losses), with the extraction of as much beam energy as possible. Producing the technology of power generation needed for the two-beam acceleration scheme.

• Demonstrate the stability of the decelerated beam and the produced RF power by the PETS.

• Benchmark the simulation tools in order to validate the corresponding systems in the CLIC nominal scheme.


TBL + BPM SpecificationsMain features of the Inductive Pick-Up (IPU) type of BPM:•less perturbed by the high losses experienced in linacs;•the total length can be short; •it generates high output voltages for typical beam currents in the range of amperes; •calibration wire inputs allow testing with current once installed•broadband, but better for bunched beams with short bunch duration or pulse

IPU type of BPM suitable for TBL

2 BPS prototypes design and constructed at IFIC (scaled version of IPU DBL of CTF3)

TBL beam time structure GDE Meeting Madrid 20

BPS Mechanical Assembly

Vacuum assembly: ceramic tube with Kovar collars at both ends, one collar TIG welded to the downstream flange, and the other one electron welded to a bellow and a rotatable flange (~10-10 mbar l/s High Vacuum)

Ferrite cylinder

Cooper body

PCB plates

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BPS Basic Sensing Mechanism

•Four Outputs (V+,V-, H+,H-) with two Calibration inputs (Cal+, Cal-)•Difference signals (Δ) normalized to sum signal (Σ) (proportional to beam position coordinate) xV α ΔV /Σ Vertical plane xH α ΔH /Σ Horizontal plane

where: ΔV ≡ (V+ − V-); ΔH ≡ (H+ − H−); Σ ≡ (V+ + H+ + V− + H- )

Primary transformer electrode

Longitudinal cross-section view


BPS Frequency Response

Induced current/signal Pulse deformation

ωlow = R/L or flow = R/ 2𝜋L ωhigh = 1/RCS or fhigh = 1/2 RC𝜋 S

τdroop =1/ ωlow and τrise =1/ωhigh

τdroop ~ 102 tpulse τrise ~ 10-2 tpulse

to let pass the pulse without deformation (droop time very important for ADC sampling)


BPS Electric Model

• High cut-off frequency: Fixed by secondary Cs for all cases•Low cut-off frequencies:I)Centered wire: Balanced wall image curentII)Displaced wire: Unbalanced wall image current (low frequency coupling)

fhigh = 1/2 R𝜋 eCS

Cut-off Frequencies:

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fL = (RP+RC)/2𝜋L

fL = (RP+RC)/2 L𝜋

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BPS Electronic Design


BPS Electronic Design

Characteristic Output Signal Levels:

Vsec = (Σ/IB) Ielec with: (Σ /IB) = (RLoadRS1/(RS1+RS2+RS1)N) = 0.55Ω for design values:

RLoad = 50 Ω, RS1 = 33 (13) Ω, RS2 = 18 (0) Ω (Ver. 2) N = 30 turns

PCBs Schematics and Output relation

For a beam current of: IB = 30AΣ = 16.5 V outputs sum

Vsec = Σ /4 = 4.125V centered beam

||ΔV||max = ||ΔH||max = Σ /2 = 8.25V beam

at electrodes


BPS Readout Chain

Amplifier developed at UPC

Digitizer/ADC developed at LAPP(Annecy)

Both designs must be rad-hard


BPS Characterization Tests (Wire-Test)

Sensitivity, Linearity and Frequency response

carried out during several short stays at CERN, in the AB/BI-PI[1], where the wire testbench is placed, and it has been previously used for testing and calibrating BPMs for the Drive Beam Linac (DBL) of the CTF3.

Tests carried out during several short stays at CERN, in the AB/BI-PI* Labs.

Testbench used to characterize the BPMs for the Drive Beam Linac (DBL) of the CTF3

Accelerator an Beams Department/ Beam Instrumentation Group – Position and Intensity Section GDE Meeting Madrid 28

BPS: Sensitivity test (Ver. 1)

Sensitivity Electric Offset

Sensitivity for V,H planes Electric Offset for V,H planes

Linear fit equations

SV = (41.09±0.08)10−3 mm−1

SH = (41.53±0.17)10−3 mm−1 EOSH = (0.15±0.02) mm

EOSV = (0.03±0.01) mm


BPS: Linearity test (Ver.1)

Linearity errorOverall Precision/Accuracy

σV = 78 μm

σH = 170 μm

i) Low current in the wire (13 mA) vs beam 32 Aii) Misalignment in the horizontal electrodes

σTBL < 50μm

Typical S-shape

BPS above specs:

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Cut-off frequencies:

BPS: Frequency Response test (Ver.1)Output electrodes ΔV, ΔH and Σ

Wire

Pos

: Cen

ter

Wire

Pos

:+8m

m V

,H

fhigh > 100 MHz τrise < 1.6 ns fLΣ = 1.76 KHz τdroop Σ = 90s

fLΔ ≡ fLΔH = fLΔV = 282KHz τdroop Δ = 564ns

Bandwidth specs: 10KHz-100MH tpulse=140ns

Coupling at low frequency(no beam variation)


BPS: Pulse Response and Calibration (Ver.1)

fLΔ[cal] =180 KHz < fLΔ =282 KHz (difference is about 100 KHz)

Represents a problem for the amplifier compensation in the Δ channels (lower fLΔ), because the same compensation designed for the fLΔ will be applied when exciting the calibration inputs to fLΔ[Cal] (bad pulse for calibration ,overcompensation)

Compensation frequency at the lower one fLΔ[Cal] gives a calibration pulse good flatness and wire-beam pulse flat enough for TBL pulse duration

τdroop Δ [cal] = 884 ns

τdroop Δ = 564 ns

τdroop Σ = 90 μs

τdroop Σ [Cal] = 90 μs


BPS: Characterization Table (Ver.1)

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BPS1 Sensitivity and Linearity Parameters

Vertical Sensitivity, SV 41.09 mm-1

Horizontal Sensitivity, SH 41.43 mm-1

Vertical Electric Offset, EOSV 0.03 mm

Horizontal Electric Offset, EOSH 0.15 mm

Vertical overall precision (accuracy), σV 78 μm

Horizontal overall precision (accuracy), σH 170 μm

BPS1 Characteristic Output LevelsSum signal level, Σ 16.5 V

Difference signals max. levels, ||ΔV||max, ||ΔH||max 8.25 V

Centered beam level, Vsec (xV = 0, xH = 0) 4.125 V

BPS1 Frequency Response (Bandwidth) Parameters

Σ low cut-off frequency, fLΣ 1.76 KHz

Δ low cut-off frequency, fLΔ 282 KHz

Σ low cut-off frequency calibration, fLΣ [Cal] 1.76 Hz

Δ low cut-off frequency calibration, fLΔ [Cal] 180 KHz

High cut-off frequency, fhigh > 100 MHz

High cut-off frequency calibration, fhigh [Cal] > 100 MHz

BPS1 Pulse-Time Response Parameters

Σ droop time constant, τdroopΣ 90 μs

Δ droop time constant, τdroopΔ 564 ns

Σ droop time constant calibration, τdroopΣ [Cal] 90 μs

Δ droop time constant calibration, τdroopΔ [Cal] 884 μs

Rise time constant calibration, τrise < 1.6 ns

Rise time constant calibration, τrise [Cal] < 1.6 ns

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BPS: Conclusions

• A set of two BPS prototypes with the associated electronics were designed and constructed.

•The performed tests yield:• Good linearity results and reasonably low electrical offsets from the mechanical center.• Good overall-precision/accuracy in the vertical plane considering the low test current; and, a misalignement in the horizontal plane was detected by accuracy offset and sensitivity shift.• Low frequency cut-off for Σ/electrodes signals, fLΣ, and high cut-off

frequency, fhigh, under specifications.

• Low frequency cut-off for Δ signals, fLΔ, determined to perform the

compensation of droop time constant, τdroopΔ, with the external amplifier.


BPS: Future Work

• Open issues for improvement in the BPS2 monitor prototype:o correct the possible misalignments of the horizontal plane electrodes suggested in the linearity error analysiso check if overall-precision below 50μm (under TBL specs), with enough wire current New wire testbench at IFICo study the different low cut-off frequencies in the calibration, fLΔ[Cal],

and wire excitation cases, fLΔ

• Test Beam of the BPS1 in the TBLResolution at maximum current.

• BPS series production and characterization (15 more units). The new wire testbench will allow higher currents, accurate (anti-vibration and micro-movement system) and automatized measurements.


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BPS: Future Work

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Sketch of new IFIC Wire Testbench (under construction)

x/y range 50x50 mmResolution 0.1 mPrecision 0.7 m

Main Future projectsATF-ATF2: Beam Instrumentation design and construction:

• BPM’s supports with micromovers for FONT4 (KEK, JAI)

• multi OTR (KEK, SLAC)

ILC: BDS instrumentation studies

LHC: non-linear collimation options for sLHC (SPS experiments) (EUCARD)

IFIMED: Imaging and Accelerators applied to Medicicine

• Monitoring of secondary beams (beam position and size) (CERN; LLR, CNAO)

• Cyclinacs applications (TERA, CTF3) CABOTO: Carbon Boster for Therapy in Oncology



Documents

R&D for Future Accelerators at IFIC Scientific Staff: A. Faus-Golfe, C. Alabau, J.J. García, S. Verdu, J. Alabau Technical Staff: J.V. Civera, C. Blanch