10-4-06 ap department meeting 1 ilcdr06 workshop highlights e. gianfelice

10-4-06 AP Department Meeting 1

ILCDR06 WorkshopHighlights

E. Gianfelice

https://wiki.lepp.cornell.edu/ilc/bin/view/Public/DampingRings/CornellWorkshopTalks

Date Event ILCTA@NML 2

ParticipantsCornell University:• Michael Billing, James Crittenden,

Gerry Dugan, Don Hartill, Robert Meller, Mark Palmer, David Rice,David Rubin, David Sagan, Levi Schachter, Eugene Tanke, Jeremy Urban

SLAC:• Karl Bane, Craig Burkhart, Yunhai Cai,

Anatoly Krasnykh, Cho Ng, Mauro Pivi, Gennady Stupakov, Lanfa Wang

LBNL:• Christine Celata, Stefano De Santis,

Ina Reichel, Marco Venturini, Michael Zisman

ANL:• Michael Borland, Louis Emery,

Katherine Harkay, Aimin Xiao

KEK:• Kazuhito Ohmi, Yusuke Suetsugu,

Junji Urakawa

INFN-LNF:• Susanna Guiducci, Fabio Marcellini

DESY:• Ferdinand Willeke, Guoxing Xia

FNAL:• Panagiotis Spentzouris, Eliana

Gianfelice-Wendt

• Gerald Codner (CLASSE), Robert Macek (TechSource/LANL), Thomas Mattison (Univ. of British Columbia), Art Molvik (LLNL), George Gollin (University of Illinois), Andy Wolski (University of Liverpool/Cockcroft Institute).


Goal

Opening talk by A. Wolski:• Not justified double addressed topics worry

funding agencies. • The GDE R&D Board has charged a 10

members task force (S3, chair: A.Wolski)

for coordinating efforts. • S3 suggested meetings focused on the most

design affecting issues (kickers, e-clouds, impedance driven instabilities) and comparisons between codes and possibly with measurements.


Two major changes wrt November 2005 baseline:

• one e+ DR (instead of two)• 650 MHz RF frequency (instead of 500)

Under re-consideration:• length• one tunnel for both DRs


Impedance driven instabilities Experiments

K.Harkay showed results from APS (impedance computations + simulations vs. measurements). Agreement between theory and measurement is evaluated as ``70 %'', but for the microwave instability 80% larger than computed impedance was needed to get order of magnitude right! Not comforting for the design of new components.

Time demanding 3D-codes going to be used for a better estimate of APS components impendance. J.Urakawa summarized the past years attempts of bunch length

measurement and microwave instability detection at ATF in presence of IBS.

Large discrepancies between some theoretical (Bane) and experimental evaluations of the machine impedance. With new detectors (Silicon Bolometer, Schottky Barrier Diode) CSR

has been detected, but no microwave instability.

K.Bane reported briefly on the “puzzling” experience with the 3 SLC DR designs.


SLC damping ring summarySLC damping ring summary

original 1.1e10 1.5e10

old 2.0e10 3.0e10

new 2.0e10* 1.5e10

threshold version calculated measured

“sextupole” mode

quadrupole mode

*if add 2nH (0.1) inductance• How to understand: from old to new ring reduced the impedance and threshold dropped? old, inductive ring—strong mode—tune spread—weak modes Landau damped new, resistive ring—weak mode—little tune spread—no Landau damping

• Note: old ring, SLC operation limited to 3e10, new ring—5e10


Current dependence


Impedance driven instabilities

Code developments

M. Borland presented the capabilities of elegant for ``integrated modeling'': one code for (almost) all.

The current DR design does not meet the Boussard (crude) criterion (for long bunches)!

New tools for studying microwave instabilities has been presented by

G. Stupakov (linearized Vlasov-FP equation solver in time domain, accurate but time consuming), S.Heifets and K.Bane (tracking, fast but prone to noise)

and M.Venturini (Vlasov equation).



• Consistent with Heifets macroparticle simulationsfor Broad-Band resonator model (Venturini).

Current Threshold

Vlasov calculationVlasov calculation

Macroparticlesimulation

Macroparticlesimulation

No

rmal

ized

cu

rren

t

Macroparticle simulation includes radiation effects



• Coasting beam: Oide-Yukoya frequency domain VFP solver indicates instability when there is none

Eigenvalue spectrum below (theory) threshold

• Theory says all eigenvalues should be on real axis…

Eigenvalue spectrum

above (theory) threshold

only this eigenvalue

corresponds to a reallyunstable mode


Compare options: simulations recent historyCompare options: simulations recent historyCompare options: simulations recent historyCompare options: simulations recent history

Cloud density near (r=1mm) beam (m-3) before bunch passage, values are taken at a cloud equilibrium density. Solenoids decrease the cloud density in DRIFT regions, where they are only effective. Compare options LowQ and LowQ+train gaps. All cases wiggler aperture 46mm.

e- clouds


e- clouds

To be addressed:

e- production suppression through clever vacuum chamber design

surface material and conditioning to reduces SEY

clearing electrodes design compatible with

heat load and beam stability


e- clouds• Some past experience• Laboratory measurements: conditioning: SEY~1. In vacuum de-conditioning brings up SEY ~ 1.3• KEKB tests: conditioning in situ. [Cross-benchmarking with simulations gives low SEY~1]• SPS-CERN: • conditioning in situ in the SPS. Minimum measured conditioned surface

SEY~1.5. De-conditioning effect. Electron cloud effects decreased in time• PSR-LANL: conditioning slow in time and de-conditioning. Still an issue. Measuring electron

cloud since 1989! • Dafne: Luminosity reach is limited. (Aluminum SEY ~2.0 after conditioning)• Bfactories: KEKB: smaller bunch spacing is limited by electron cloud. Still after years PEP-II: no problem up to 2.7A. • Ongoing tests KEKB (effect of solenoid and fill pattern, see Ohmi presentation), CESRc (no effect of solenoids &wigglers observed, see Rice presentation), Dafne, PEP-II, PSR (e- production and trapping at quads, see Macek presentation).


Ongoing chamber projects at SLAC:

e- clouds

CLEARING ELECTRODES

BEND PEP-II LER PR12 2007 Design

FINS TRIANG. BEND PEP-II LER PR12 2007 Design

TEST in LOCATION Ready for INSTALLATION

Status

SEY TESTS STRAIGHT PEP-II LER PR12 November 2006Ready

FINS RECTANG. STRAIGHT PEP-II LER PR12 November 2006

Coating of extruded Al chambers

Next chamber projects:

M. Pivi, SLAC


e- clouds

• Model for MWS • Head (W:8 mm,T:7 mm, L:90 mm)– Copper, 10 mm from beam

• Support – BN (W: 4 mm, T: 6mm)

• r = 4.0, tan= 0.0008– Al2O3 (W: 4 mm, T: 4mm)

• r = 9.0, tan = 0.0001– Thin layer (t = 0.1mm) with

conductivity (), as a coating• Duct

– 94, L: 300 - 500 mm• SiC

– Deby first-order dispersion– s= 110, = 14, = 110-9s

Port 1

Port 2

Beam duct SupportHead

SiC

SiC

• Calculation– S11between Port 1 and Port 2

• Antenna: 10 mm– Frequency mode

is

r

1

)()(

Debye type


e- clouds SimulationsEfforts of improving the e- clouds simulations.

Upgrade of ECLOUD and HEADTAIL. New 3D self consistent simulation code by W.Bruns being developed and tested against ECLOUD.

WARP-POSINST (LBNL): 3D (and 2D), any boundary, adaptive mesh size, self consistent, benchmarked by the High Current Experiment (HCX) at LLNL.

Simulations of e- clouds in wigglers with

CLOUDLAND (Lanfa Wang, SLAC).


e- build-up for ILC 2(1)x6 km DR – 2 (ECLOUD)

example simulationscentre density (m-3) vs. time (s),primary photo-electron rate:d/ds= 0.001 m-1,bunch train followed by gap,arc & straight, log scale

max=1.3, 14.4 ns

max=1.5, 14.4 ns max=1.3, 7.2 ns

thr

thr thr


e- clouds

WARP

POSINST

field calculator

ion mover

image forces

electron sourcemodules

kicks from beam

diagnostics

lattice description

xi, vi

interpreter&

user interface

electron mover


e- clouds

1. 2D vs. 3D

2. Head-tail instability

3. Effect of gaps and resultant ecloud

4. Electron cloud & beam in wiggler

Processor hours per run

120

5600

16,000

60,000 - 270,000

CPU time is estimate-- depends on problem.

Computer Time will to be Requested (‘07) for WARP-POSINST


CLOUDLAND 3D PIC code for e-cloud (PRST-AB 124402)

Simulation Key parameters(beam,ring,SEY,electrode, …) Mesh Generator

Magnetic and electric fields input

Space charge solverCharge meshUpdate particle positions

Advance particle positions using the new beam and e-cloud space charge fields

Preliminary electron generator when beam passing

Secondary electron generator

Preliminary electron generator

Wake field Instability code

Future plan --Parallelize for consistent instability study


Train gap effect (2767bunches)

-200 -100 0 100 20010

8

109

1010

1011

1012

1013

Z (mm)

(

m-3

)

Bunch Train gaps reduce the electron cloud density by a factor of 10

0 20 40 60 80 100 12010

9

1010

1011

1012

Bunch ID

e (

m-3

)

average densitycentral density

0 20 40 60 80 100 12010

9

1010

1011

1012

1013

1014

Bunch ID

e (

m-3

)

One train

Short train


Comparison with dipole

0 20 40 60 80 10010

9

1010

1011

1012

1013

1014

Bunch ID

e (

m-3

)


0 20 40 60 80 100 12010

9

1010

1011

1012

Bunch ID

e (

m-3

)


Dipole, B=0.194TWiggler

There is a lower electron density in Wigglers (one order)! (assuming the same initial electrons rate )


e-clouds

Experimental tool at LBNL for studying

e- production and effect of clearing electrodes

(see Molvik presentation).


A tool for ecloud experiments at LLNL

INJECTOR MATCHINGSECTION

ELECTROSTATICQUADRUPOLES

MAGNETICQUADRUPOLES

Focus of CurrentElectron Cloud Experiments

(2 m length)

1 MeV K+, 0.18 A, t ≈ 5 s, 6x1012 K+/pulse

low energy heavy ions

2 m


ESQ injector

Marx

matching

10 ES quads

diagnostics

diagnostics

ESQ injector

10 Electrostatic quads

diagnostics

4 Magnetic quads Parameters

K+ Beam 0.2 - 0.5 Amp 1 - 1.7 MeV 4.5 s pulse


MA4MA3

8 “paired” Long flush collectors (FLL): measures capacitive signal + collected or emitted electrons from halo scraping in each quadrant.

3 capacitive probes (BPM); beam capacitive pickup ((nb- ne)/ nb).

2 Short flush collector (FLS); similar to FLL, electrons from wall.

2 Gridded e- collector (GEC); expelled e- after passage of beam

2 Gridded ion collector (GIC): ionized gas expelled from beam

BPM (3)

BPM

FLS(2)

FLS

GIC (2)

GIC

Not in service

FLS

GECGEC


ILC DR Test FacilitiesNew propsed DR Test Facilities:

M.Palmer presented the plan for transforming CESR in a ILC DR Test Facility (starting in 2008, 50% time sharing with SR experiments, Touschek lifetime: 7 minutes).

F.Willeke presented the plan for transforming HERA-e into a ILC DR Test Facility.

Suetsugu speculated about the possibility of transforming KEKB into a DR Test Facility (if Super KEKB get not support from the japanese HEP community?).


1) What Can CESR Offer?

CESR offers:– The only operating wiggler-dominated storage ring in the

world– The CESR-c damping wigglers

• Technology choice for the ILC DR baseline design– Flexible operation with positrons and electrons– Flexible bunch spacings suitable for damping ring tests

• Presently operate with 14 ns spacing• Can operate down to 2 ns spacings with suitable feedback

system upgrades– Flexible energy range from 1.5 to 5.5 GeV

• CESR-c wigglers and vacuum chamber specified for 1.5-2.5 GeV operation

• An ILC DR prototype wiggler and vacuum chamber could be run at 5 GeV

– Dedicated focus on damping ring R&D for significant running periods after the end of CLEO-c data-taking

– A useful set of damping ring research opportunities…• The ability to operate with positrons and with the CESR-c

damping wigglers offers a unique experimental reach

Date Event ILCTA@NML 31-1

0

1

2

3

4

5

6

-5 10-9 0 5 10-9 1 10-8

FID(FPG-3000M) Waveform

Vol

tage

(kV

)

Time(s)

Pulse generator

Specifications

Amplitude at 50 ohm : 5 kVRise time : 1-1.4 nsPulse width at 50% of amplitude : 2-3 nsMaximum Pulse Repetition Frequency in burst mode : 3 MHz

FID Technology has very fast and high repetition rate pulse generators. The specification meets our requirements for the high voltage pulse source. We tested the kicker performance by using the pulse PS.


Beam kick experiment at ATF DR

The kicker pulse is applied to the strip-line electrode when the beam goes through the electrode.The beam kick is observed by a turn-by-turn BPM as the amplitude of the oscillation of the betatron frequency component.The kick effect is measured by scanning the pulse timing precisely.


Measurement result of FPG5-3000MThe achieved resolution is 0.2rad.

Rise time~3.2nsKick angle ~91rad(calc. 94.7rad)

Expanded horizontal scale

0

20

40

60

80

100

10 12 14 16 18 20

Pulse timing v.s. kick angle(FID FPG-3000M)

Kic

kAng

le(u

rad)

Delay(ns) Time

0

20

40

60

80

100

0 5 10 15 20 25 30

Pulse timing v.s. kick angle(FID FPG-3000M)

Kic

kAng

le(u

rad)

Delay(ns) Time


• Comments (Zisman)– existing “FID” tests seem to have been DSRD

pulsers!– concerns about robustness– single-source issue

– Alternative solutions need to be studied.A working kicker design meeting impedance and

vacuum properties is still to be demonstrated. HV feed-through are critical.

– Consider use of an injection bump for relaxing kicker requirement: is it feasible?

10-4-06 ap department meeting 1 ilcdr06 workshop highlights e. gianfelice

Documents

microwave instabilities

design of new components

new tools

computed impedance

machine impedance

old ring

michael borland

karl bane