Webex

Parameters for electron cloud build-up and

instability simulations 2012

ILC DR Electron Cloud Working Group

Feb 29, 2012

February 15, 2012 ILC DR Working Group

Link to 3.2 km DR files

ILC Damping Ring wiki website:

5Hz lattice (baseline) files:

• https://wiki.lepp.cornell.edu/ilc/bin/view/Public/Dampi

ngRings/#TDP_II_Baseline_Lattice_Vers_AN1

10Hz lattice files:

• https://wiki.lepp.cornell.edu/ilc/bin/view/Public/Dampi

ngRings/#TDP_II_Baseline_Lattice_Version

Lattice design by David Rubin, Cornell U.

February 15, 2012 ILC DR Working Group

David Rubin, Cornell U.

February 15, 2012 ILC DR Working Group

wiggler arc arc injection /

extraction

February 15, 2012 ILC DR Working Group

February 15, 2012 ILC DR Working Group

Magnets

Wigglers strength 1.5T at 5 Hz and 2.16T at 10Hz

max

February 15, 2012 ILC DR Working Group

Build-Up Simulations 3.2 km DR

Section Vacuum

chamber radius

(from RDR)

Antechamber

full height

Beam sizes

sx,sy

(mm)

Surface +

mitigation

peak SEY

Arc Dipole 25 mm 10 mm 215, 6.9 TiN + Grooves 1

Arc Quadrupole 25 mm 10 mm 290, 6 TiN 1

Arc Sextupole 25 mm 10 mm 290, 6 TiN 1

Arc Drift 25 mm 10 mm 290, 6 TiN + solenoid 1

Quadrupole in straigth 25 mm none 110, 6.4 TiN 1.2

Drift in straigth 25 mm none 110, 6.4 TiN + solenoid 1.2

Wigglers 23 mm 20 mm 80, 5.5 Cu + clearing

electrodes

1.22

Quadrupole in wiggler

region

23 mm 20 mm 80, 5.5 TiN 1

Drift in wiggler region 23 mm 20 mm 80, 5.5 TiN + solenoid 1

Electron cloud build-up simulation parameters:

arc

s

str

aig

hts

w

igg

ler

February 15, 2012 ILC DR Working Group

Cloud Density

From build-up simulation, we need to extract the

value of the cloud density:

1. After build-up and several bunch passes, when

cloud density reaches an equilibrium value

2. Cloud density JUST BEFORE electron cloud

pinching (at the head of the bunch)

3. Cloud density “near the beam” (20 sx, 20 sy)

February 15, 2012 ILC DR Working Group

Fill pattern

February 15, 2012 ILC DR Working Group

Secondary emission yield for TiN and Copper

surfaces to assume in simulations

• Our mitigation recommendation plan for most of the

ring to be coated with TiN (on Al substrate)

• Wiggler regions consists of Cu and clearing

electrodes

• Selected TiN and Cu samples from in-situ

measurements at KEK-B, CesrTA and PEP-II:

– processed TiN from CesrTA (SEY peak ~1)

– processed Cu from PEP-II (SEY peak ~1.2)

February 15, 2012 ILC DR Working Group

SEY for processed TiN film coating

email Walter Hartung (wh29@cornell.edu) or Joe Calvey (jrc97@cornell.edu) for data files

TiN CesrTA - “horizontal sample” 0 degree

February 15, 2012 ILC DR Working Group

TiN with peak SEY~1.2 to simulate regions with less conditioning only: i.e. drift and

quadrupole in straights

(Note: drift and quadrupole in wiggler regions should use instead TiN with SEY~1).

SEY for non-fully processed TiN film coating

Fitting the low energy

part of the spectrum

might be improved …

TiN CesrTA - 45 degree sample

February 15, 2012 ILC DR Working Group

SEY for processed Copper surface

Peak 1.22, Energy at peak ~ 570 eV

C:\\ P

hys

ics S

EY

\\ Mauro

_F

red _

SE

Y _

Data

_ 2

003-2

008\\ A

SC

II TR

AN

SLA

TE

D F

ILE

S \\ 0

06061.D

AT

PEP-II beam parameters

Beam Energy, E (GeV) 3.1

Relativistic Factor, g 6066.5

Nominal Beam Current, I (A) 4.7

Dipole Magnet Field, B (Tesla) 0.765

Critical Energy, Ecrit (keV) 4.8

Dipole Magnet Arc Section, Dq (mrad) 32.7

Dipole Arc Section of photons hitting sample, Dq (mrad) 7.5 10-6

Distance of last bend magnet to SEY station location, (m) 10.1

Bunch length (mm) 12

Spacing between bunches (ns) 4.2

Transverse beam size at the sample (x/y) (μm) 228/840

zoom at 10-300 eV energy

email: mpivi@slac.stanford.edu for data file

February 15, 2012 ILC DR Working Group

Fitting data with POSINST model to SEY of

“processed TiN” coating

Walter Hartung Cornell U.

The fitted parameters for the horizontal

sample are:

delta hat ts = 0.73

E hat ts = 370 eV

s = 1.32

and the fitted parameters for the 45

degree sample are:

delta hat ts = 0.95

E hat ts = 330 eV

s = 1.25

February 15, 2012 ILC DR Working Group

Photon Distribution and Photoelectric Yield Models

• The photon distribution in the ILC DR is supplied by

Synrad3D simulations (see attached Gerry Webex

presentation February 29, 2012.)

Link to photon distribution data: …

contact Gerry for more information

• Photoelectric yield (PY) model is similar in ECLOUD and

POSINST codes.

– Low energy truncated Gaussian distribution available to

both codes (Cornell version of POSINST) or Lorentzian with

high energy tail. CesrTA tune data not very sensitive to

different models.

– CLOUDLAND needs to include similar PY model

Wiggler Chamber with Clearing Electrode

• Thermal spray tungsten electrode and Alumina insulator

• 0.2mm thick layers

• 20mm wide electrode in wiggler

Joe Conway – Cornell U.

Dipole Chamber with Grooves

• 20 grooves (19 tips)

• 0.079in (2mm) deep with 0.003in tip radius

• 0.035in tip to tip spacing

• Top and bottom of chamber

Joe Conway – Cornell U.

SEY of Grooved Surface in Dipole magnet(b=2.28kG)

-2 -1 0 1 20

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

X (mm)

Y (

mm

)

Groove shape used in simulation

0 500 1000 1500 20000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Energy (eV)

SE

Y o

f g

roo

ve s

urf

ace

0=1.8

0=1.0

Simulated SEY of Grooved Surface

1st case: Sey0=1.0, emax=570eV; (Processed TiN);

2nd case: Sey0=1.8, emax=250eV; (Un-processed TiN ,before installation in CesrTA)

Lanfa Wang, SLAC

Simulation of grooved surface

February 15, 2012 ILC DR Working Group

Instability Simulations

• Use cloud density from build-up simulations

• Beam-cloud interactions:

- First use 40 interaction points/turn

- Then use a realistic MAD lattice at input

• Deliverable: define the emittance increase and growth rate

for cloud density extracted by the build-up simulations with

mitigations implemented.

February 15, 2012

Electron cloud assessment for TDR

Global Design Effort 20

ILC DR simulations ACTION ITEM 2012:

• Provide ILC DR "wall" file for Synrad3D - Ongoing

• Validate ILC DR "wall" input file for Synrad3D - Gerry Dugan, Laura Boon

• Benchmark Synrad3D with data - Jim Crittenden; end of January

• Photoelectron ILC DR Synrad3D simulations - Gerry Dugan, Laura Boon, mid-Feb

• Post DTC03 lattice and parameters list - David Rubin, ASAP

• Provide beam parameters and SEY models for simulations - Mauro Pivi, by mid-February

• Build-up simulations BEND with TiN and GROOVES - Venturini / Furman, mid-March

• Build-up simulations DRIFT: 1) fully & 2) partially conditioned - Jim Crittenden, by mid-March

• Build-up simulations QUADRUPOLE and SEXTUPOLE - Jim Crittenden, by mid-March

• Benchmark build-up simulations for QUADRUPOLE - Lanfa Wang, by mid-March

• Build-up simulations WIGGLER (as BEND) with cl. ELECTRODES- Lanfa Wang, by mid-March

• Instability simulations for DTC03 - Mauro Pivi, by mid-March

• Write up simulation results for TDR: total (3) paragraphs - All, by mid-April

February 15, 2012

Supporting slides …

February 15, 2012

• Preliminary CESRTA results and simulations suggest the possible presence of

sub-threshold emittance growth - Further investigation required

- May require reduction in acceptable cloud density a reduction in safety margin

• An aggressive mitigation plan is required to obtain optimum performance from

the 3.2km positron damping ring and to pursue the high current option

ILC Working Group Baseline Mitigation Recommendation

Drift* Dipole Wiggler Quadrupole*

Baseline

Mitigation I TiN Coating

Grooves with

TiN coating

Clearing

Electrodes TiN Coating

Baseline

Mitigation II

Solenoid

Windings Antechamber Antechamber

Alternate

Mitigation NEG Coating TiN Coating

Grooves with TiN

Coating

Clearing Electrodes

or Grooves

*Drift and Quadrupole chambers in arc and wiggler regions will incorporate antechambers

Summary of Electron Cloud Mitigation Plan

Global Design Effort 22

Mitigation Evaluation conducted at ILC DR Working Group Workshop meeting

M. Pivi, S. Guiducci, M. Palmer, J. Urakawa on behalf of the ILC DR Electron Cloud Working Group

February 15, 2012

Electron cloud ILC Damping Ring

simulations for Technical Design Report

TDR 2012

Global Design Effort 23

• The goal is to validate mitigations for the ILC DR.

• Build-up simulations should include “Baseline

Mitigation I” and “Baseline Mitigation II” as in

previous slide

• For the TDR, we will assume defined SEY values

for TiN and Copper, i.e. (given the tight deadlines

for delivering the results to the TDR) we will not

scan the SEY as it was done in the previous

simulation campaign.

February 15, 2012 ILC DR Working Group

February 15, 2012 ILC DR Working Group

Beam Sizes

wiggler arc arc injection /

extraction straight

February 15, 2012 ILC DR Working Group

February 15, 2012 ILC DR Working Group

Peak

SEY

before

Peak

SEY

after

Sample

position

respect to

SR fan

Electron

dose De

[mC/mm2

]

Photon

dose Dph

[ph/mm2]

Time

frame in

the -II

beam line

Equivalent

Integrated

beam current

[A hour]

Additional

Notes

TiN/Al 1.77 0.95 0 degree 910 8.45E+20 22Dec06 to

26Mar07

2198 Still SEY < 1

after 1000h

stand-by in

vacuum

TiN/Al 1.71 0.92 45 degree 910 - - - 22Dec06 to

26Mar07

2198 SEY < 1 after

1000h stand-by

in vacuum

NEG

TiZrV/Al

1.33* 1.09 0 degree 1183 1.06E+21 04Dec07 to

27Feb08

2767 *sample was

heated before

installation

Cu 1.8 1.22 0 degree 902 6.92E+20 27Feb08 to

08Apr08

1799

Stainless

steel

1.85 1.3* 45 degree 1667.5 - - - 15Jun07 to

24Sep07

3388 *measured 500h

after beam stop

Al 3.5 2.4 45 degree 2085 - - - 24Sep07 to

08Apr08

4566

PEP-II samples in-situ conditioning. Summary:

Will use the processed copper sample data from Pep-II

SEY for processed Cu surface - DR wiggler region

M. Pivi et al. Nuclear Instruments and Methods in Physics Research A 621 (1-3), 47–56, (2010).