Dogleg Beam-loading Experiment

Status and plans

Dogleg Beam-loading Experiment

J.L. Navarro (CERN), for the Dogleg Team

Workshop, 3 – 7 February 2014

J.L. Navarro. CLIC Workshop, 3 - 7 January 2013

Outline

- What are we studying in dogleg and Why?

- The Dogleg experiment layout

- Current status…: Phase I and results

- …and plans: Phase II

- Summary

2/22


Where…?

The study is focused on the accelerating structures of the Main Beam Linac

• Traveling waves cavities• Nominal gradient ~ 100 MV/m• Nominal RF pulse length ~ 240 ns (160 ns flat top)• Peak Power ~ 61 MW• Max. Surf. Field ~ 230MV/m

3/22


What and Why?

Strong Accelerating fields (~100 MV/m)

Problem of Break Downs (BD): Very fast (10 ns – 100 ns) and localized dissipation of stored energy in the structure.

Luminosity Reduction:

Max DB rate allow for CLIC specifications:3 10-7 BD pulse-1 m-1

T24TD18T18TD24TD24r05TD26CC

4/22

Unloaded Accelerating Gradient MV/m

Log(

BDR)

1/p

ulse

/m

Undesired effects:• Loss of acceleration• Damage in the structure• Kick in the beam• …


CLIC nominal

Unloaded

Beam loading effect

BD never studied in loaded structures

Unloaded

Loaded

Curr

ent i

ncre

ase

Beam Loading modifies the gradient distribution along the structure

5/22


The Dogleg experiment

Two phases experiment:I. Beam only:

a) Optic designb) Hardware installationc) Beam commissioning

II. RF + Beam (middle 2014):a) RF commissioningb) Structure conditioningc) RF + beam studies

Done

CERN’s T24 (12WNDSvg1.8 KEK N1)Inner volumeThanks to A. Grudiev for HFSS model

Main goal: Measure and comparison (unloaded vs loaded) of the BD rate in a T24 structure

Tapered linearlyNot Damped2 coupling cells + 24 cells

6/22


Experiment layoutExperiment located in the Dogleg Line of the CTF3 Linac (old PETS Line)

Beam side: CTF3 Drive Beam modified to mimic CLIC main beam Pulse compression to reach ~125 MeV at structure Nominal current of ~1.2 A Pulse length up to 250 ns

RF side: 90 MW RF power delivered by XBox1 35 Meters of low loss waveguide 60 MW RF power at the structure

Instrumentation side: Fixed 6mm collimator to protect the structure BPM upstream and downstream Movable slit to clean up beam

XBox1

Dogleg

Movable slitUpstream BPM

CollimatorStructure

Downstream BPM

7/22


RF wave guide installation

CTF2 CTF3Xbox1 wall

0.87 0.8

• The round group delay time is 230 ns (~35 m).• To provide nominal CLIC RF pulse, XBOX1 klystrons needs to deliver 36 MW x

1.5s

S21 Reconstructed(Xiaowei Wu)

8/22

Overall waveguide

efficiency ~ 67%


Optics design

0.0 2. 4. 6. 8. 10. 12. 14. 16. 18. 20.s (m)

0.0

10.

20.

30.

40.

50.

60.

βx(

m),

βy(m

)

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

Dx

(m)βx βy Dx

Objective: Transport the beam trough the Linac up to the structure requiring… - Full transmission efficiency - Minimum beam size on average inside the structure

Maximize relative distances between aperture and beam size (M. Dayyani). MAD model by F. Tecker.

Structure

Structure

Beam envelope

Re-matched

optics for

last running

Linac+dogle

g

9/22


Data Acquisition System: Phase ISISAcq card

Accelerating Structure

Diode Box

BPM 240 BPM 280

PSR (108 dBm)

PSI (108 dBm)

PER

PEI (105 dBm)

Tunel

Beam

3 dBCable ...450A (-68 dB)

3 dB

3 dB

Cable 451A (-69 dB)

Cable ...452A (-69 dB)

~40 dBm

~40 dBm

~36 dBm

Cable ...453A (-18.46 dB)

Online Software monitoring: Produced power from the beam Reflected power (Break-down) BPMs current (looses) Online BD detection

SIS 3320 250MHz 12bit ADC

10/22


Phase I Results: Running of May 2013C

P.B

HC

010

5

CP.

BP

M 0

115

CP.

QF

C 0

110

CP.

QF

C 0

130

CP.

QD

C 0

120

CP.

VP

I 012

5

CP.

BH

C 0

145

CP.

SL

H 0

107

S

Upstream and downs stream BPMs~ 90% transmission with no nominal optics

Horizontal orbit very offsetLimited by broken movable slit

Broken slit

No transmission with nominal optics due to big steering induced in the quads.

11/22


Phase I Results: Running of May 2013

Raw signal from OASIS

Input reflected channel

Output transmitted channel

Two different pulses length at ~1.3 A…

70 mV

~9 MW

… and some break down

12/22


- Theoretical prediction- BPM 240 current (before structure)- BPM 280 current (after structure)


Upstream BPM shows the correct tendency with a

systematic error in power

It suggest loses at the very end or after the structure.

13/22



3.3 dB error in upstream BPM

2.4 dB error in downstream BPM


14/22



Measured power scaled down by 3dB.

Shape reproduced……but error in calibration

15/22


Phase I Results: Running of May 2013Summary of first run:• No transmission with nominal optics• 90% with experimental optics• First RF beam induced signals and break downs observed• ~ 3dB of error in calibration• Theoretical pulse shape reproduced• Movable slit broken

During summer shutdown: The slit was repaired (mechanical parts and cabling) The surveyors measured components alignment (more than 1.5 mm for some quads) The acquisition system was recalibrated using TWT (Thanks to L. Timeo, S.F. Rey)

Thanks to S. Doebert, F. Tecker and T. Wisznowski for a great job when repairing the slit by ourselves.

16/22


Phase I Results: Running of Dec 2013We reach ~ 80% of transmission with almost the nominal optics (only one quad lowered)

As expected some quads introduce steering and needs to be realigned (done during Christmas shutdown.)

Dispersion is closed and we have some margin to improve transmission

17/22


Phase I Results: Running of Dec 2013And from the RF side:

Theoretical model fits within

experimental uncertainties

Data from May 2013

Data from Dec 2013(after DAQ recalibration)

18/22



Dogleg Beam-loading Experiment

Phase I summary: Technical problems with slit solved Successful calibration RF waveguide installed with overall RF efficiency of 67%. Acceptable (80%) transmission with nominal optics (better after realignment) Realignment of components done during Christmas shutdown

19/22

Two phases experiment:I. Beam only:

a) Optic designb) Hardware installationc) Beam commissioning

II. RF + Beam (middle 2014):a) RF commissioningb) Structure conditioningc) RF + beam studies

Phase II approaching!!

Status…

… and prospects.


Data Acquisition System: Phase II

Acqusition Board

Acquisition Board

PXI LabviewAcquisition

system (250MHz)

OASIS Acquisition

PC

Accelerating Structure

Pulse compressor 8 IQ

demodulatorsRange: ???

TWT4 KW

Klystron50 MW

IN K

LY

Unused

To HP8900D for interock

PKI

PKR

BPM 240

BPM 280

PLI

PLR

PSR (108 dBm)

PSI (108 dBm)

PER

PEI (105 dBm)

Tunel

Beam

3 dBCable ...450A (-68 dB)

TTL to NIM converter

3 dB

3 dB

Cable 451A (-69 dB)

Cable ...452A (-69 dB)

Dogleg Acq SystemJ.L. Navarro – BE/OP

S. F. Rey, L. Timeo – BE/RFDecember 2nd, 2013 – V1.2

ORGANISATION EUROPEENNE POUR LA RECHERCHE NUCLEAIRE EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH

Laboratoire Européen pour la Physique des Particules

European Laboratory for Particle Physics

Log detectors

Range:-40 to -10 dBm

-49 dB

-49 dB

-45 dB

?? dB

~40 dBm

~40 dBm

~36 dBm

TimingCX.SMEAS-RFX2

TTL to ??? converter

?? dB

?? dB

?? dB

Cable name Channel Max. P. (MW) Max. P(dBm) Coupler (dB) Power (dBm) Cable T. (dB) Power (dBm) Splitter (dB) Power (dBm) Att. (dB) Cable 2 log (dB) Input ADC (dBm)???? PKR 50 106.9897 106.9897 0 106.9897 106.9897…450A PSI 60 107.781513 48.6 59.1815125 17.9 41.2815125 3 38.2815125 49 0 -10.7184875…451A PSR 60 107.781513 48.7 59.0815125 18.1 40.9815125 3 37.9815125 48 0 -10.0184875…452A PEI 30 104.771213 49.1 55.6712125 18.5 37.1712125 3 34.1712125 45 0 -10.82878745

Cable ...453A (-18.46 dB)

20/22


Tentative Planning

Ready for and exciting dogleg

2014 campaign!

• Xbox will be connected in the next weeks

• Some time for synchronization, calibration, conditioning…

• Specific slot reserved for dogleg during summer restarting.

21/22


Thanks for your attention

M. DayyaniS. DoebertJ.L. NavarroS.F. ReyF. Tecker L. Timeo T. WisznowskiAll operators

CTF3

M. FilippovaD. GudkovP. GuyardS. LebetA. OlyuninG. RiddoneA. SamochkineI. SyratchevA. SolodkoP. De Souza

RF/PM XBOX

S. CurtA. DegiovanniG. McMonagleJ. Tagg B. WoolleyX. Wu

TE-VCS

E. Paju

Special thanks to A. Grudiev for very useful discussions and material.

22/22


Thanks for your attention

23/22

New VISTARBy D. Gamba


Backup: CLIC Nominal parameters 24/22


BackupAccelerating gradients achieved in tests.

Status: 4-9-2012

loaded

25/22

26

Structure under test:CERN’s T24 (12WNDSvg1.8 KEK N1)No damping

Backup (I. Syrachev. CLIC Workshop 2013)

27

Insertion losses of the input/output waveguide network (splitter and bends) is -0.15 dB (=0.967)

-49.32

-52.04

Calibration (I. Syrachev. CLIC Workshop 2013)

28Backup

29Backup


Phase I Results: Running of Dec 2013And from the RF side:

Theoretical model fits within

experimental uncertainties

Data from May 2013

Data from Dec 2013(after DAQ recalibration)

P[MW]=1.91 I2

P[MW]=3.17 I2

P[MW]=2.62 I2

30/22

31Dog-leg waveguide line installation status.

All the components are installed. Connected to accelerated structure and closed for vacuum. Vacuum leaks checked (tight).

Ready to be connected to XBOX1.

32RF power transmission measurements

S11 data

Short circuit(+offset)

Matched load

S21 Reconstructed(Xiaowei Wu)

Transmission (simulated)

Reflection

• The measured RF power transmission efficiency is 80%.• Reflection is below -27dB.• The group delay time is 75 ns (~23.5 m).

33

CTF2 CTF3Xbox1 wall

0.87 0.8

Overall power transmission efficiency

• The overall measured RF power transmission efficiency is 67%.• The round group delay time is 230 ns (~35 m).• To provide nominal CLIC RF pulse, XBOX1 klystrons needs to deliver 36 MW x 1.5s

Documents

Dogleg Beam-loading Experiment