Top-Up Experience at SPEAR3

• SPEAR 3 and the injector

• Top-up requirements

• Hardware systems and modifications

• Safety systems & injected beam tracking

• Interlocks & Diagnostics

Contents

3GeV Injector

BTS

5W, 1.6nA

E

W

N S

3GeV

10nm-rad

500 mA

Booster

(White

Circuit)

LINAC/RF Gun

10Hz

SPEAR3 Accelerator Complex

PXPD/XAS

SAXS/PX

XAFSNEXAFS

PX

PX

XAS/TXM

ARPES

EnvironmentXAS

CoherentSingle bunch/pulse

o Rebuild SPEAR into SPEAR3 (1999-2003)

o Operated at 100mA for ~6 years (beam line optics)

o Recently increased to 200mA

o Chamber components get hot at 500ma (450kW SR, impedance)

o 500mA program suspended because of

power load transient on beam line optics

o Instead worked to top-off mode (beam decay mode, fill-on-fill)

Top ‘off’ at SPEAR3

RF system and vacuum chamber rated for 500ma

o 13 exit ports taking SR (9 Insertion Device, 4 Dipole)

o 7 ID ports presently in „fill-on-fill‟ open shutter mode

o 4 dipole beam lines open shutter injection by end of October 2009

o Last two ID shutters fill-on-fill by June 2010

o Trickle charge 2011

Present Status

SPEAR 3 100 vs. 500 mA Fill Scenarios

lifetime = 14 h @ 500 mA

= 60 h @ 100 mA

0

50

100

150

200

250

300

350

400

450

500

0 4 8 12 16 20 24

time (hrs)

cu

rren

t (m

A)

100mA and 500mA Operation

=12ma

=180ma

100ma

500ma

~6.5 Amp-hr

delivery time = 8 hr

tfill = ~6-7 min

delivery time = 2 hr

tfill = ~1.5-2 min

SPEAR 3 500 mA Fill Scenario

lifetime = 14 h @ 500 mA

0

50

100

150

200

250

300

350

400

450

500

0 6 12 18 24

time (hrs)

curr

ent

(mA

)

delivery time = 0.5 hr

tfill = ~17 sec

SPEAR 3 500 mA Fill Scenario

lifetime = 14 h @ 500 mA

0

50

100

150

200

250

300

350

400

450

500

0 6 12 18 24

time (hrs)

curr

ent

(mA

)

delivery time = 1 min

tfill = ~0.5 sec

(or 10ms single shot)

500mA Injection Scenarios

RF

B132-102

B116-

101

B117

control

roomB118

power

suppliesSLM

room

B132-101

B120

B131

B130

3 GeV

Booster

120 MeV

linac

B140

LTB

BTS

RF

HVP

S

• Gun

o higher current

o stablize emission rate

o “laser-assisted” emission

• Linac

o restore 2nd klystron

(higher energy, feedback)

o phase-lock linac and booster rf

• Booster

o improve capture with modified lattice

o improve orbit and tune monitors

o develop fast turn-on mode

• BTS

o eliminate vacuum windows (done)

o diagnostics

• SPEAR

o add shielding, interlocks

o improve kicker response

o transverse feedback

• Beamlines

o add shielding, interlocks

o timing

Hardware Upgrades

• Vertical Lambertson septum (booster outside ring)

- operates DC, skew quadrupole added

• Three magnet bump

• ~15 mm amplitude, ~12mm separation

• Injection across three cells (sextupoles)

• Slotted stripline kickers (DELTA, low impedance)

• Transverse field dependence in K2

SPEAR3 Injection Notes

Elevation viewPlan view

Injected beam

Stored beam

Se

ptu

m w

all

Se

ptu

m w

all

With windows: ~20% beam loss No windows: ~no loss

Hardware Upgrade: BTS Windows

Huang & Safranek

Injected beam profile measurements

Turn number

Movies…

Visible diagnostic beam line

• Synchrotron oscillations measured with turn-by-turn BPMs:

• Kickers set to dump injected beam each cycle

• Injection energy stable

• Injection time varies over hours– RF cable temperature

• Develop method to measure timing with stored beam

Before correction After correction

Hardware upgrade: Injection Timing and Energy

Huang, Safranek & Sebek

V

H

mS

V

H

mS

Single shot

injection kicker transient = ~10 ms

(~0.1 ms with feedback)

• Kickers can interrupt data acquisition

o What is interruption sequence?

• depends on current ripple, beam lifetime and charge/shot

• bunch train filling needs new booster RF system

o Gated data acquisition

o Tests with beam lines no complaints

o Lots of work to match kicker waveforms

Hardware upgrade: Injection Bump Closure

Huang & Safranek

downconverter schematic

Hardware Upgrade: PEP-II Bunch Current Monitor

bunch-by-bunch processor chassis

- visible APD (ASP)- x-ray APD (CLS)

downconverter chassis

A.S.Fisher

► S-band RF gun with thermionic cathode, alpha magnet, and chopper

► Most charge during the 2 μs RF pulse stopped at the chopper

► 5-6 S-band buckets pass into the linac, single booster bucket

► SPEAR3 single bunch injection, 10Hz presently ~50pC/shot

2.856 GHz (2 s)

e- beamTungsten

dispenser-cathode

(1000 C)

1.5 cell RF gun

Hardware Upgrade: Thermionic Cathode as a Photo-Emitter

Nominal configuration

► high singe-bunch charge for top-off

- reduce beam loading in linac

- eliminate cathode back bombardment

- eliminate chopper

2.856 GHz (~2 s)

e- beam (~500ps)cold-cathode

UV or green laser

UV Green

1.5W heating

Sara Thorin/MAXLab, EPAC'08

'Turning the thermionic gun into a photo injector

has been very successful '

1.5 cell RF gun

Photo-emission cathode (cont’d)

Laser-driven configuration

Cu

S.Gierman

• Radiation Safety: the first hurdle

o AP studies to demonstrate injected beam can not escape shielding

o Many clever scenarios (dreams and zebras)

o BL shielding sufficient? (higher average current, more bremsstrahlung)

o PPS/BCS interlock modifications

o Do users wear badges?

• Efficient injection into main ring

o Injection time, charge/shot, repetition rate

The Injected Beam Safety Dilemma

Safety is complicated!

18

SPEAR3 DBA cell

Synchrotron Radiation Exit Ports

V4 MASK

V1, V2 MASKS

BPMs

H2 ABSORBER

TSPs

EDDY CURRENT

BREAK

BM-2

QFC

BM-1

220 L/S

ION PUMP

150 L/S

ION PUMP

TSP

V3 MASK

BELLOWS

BELLOWS

H1 ABSORBER H3 ABSORBER

TSP

BPM

BPM

BPM

ID BPM

ADDITIONAL

BPM SET

220 L/S

ION PUMP

84 mm

44.2

mm

34

mm

24 mm13 mm18.8 mm

ID BPM

BPM

Vacuum Chamber Construction

e- beam

photon beam

outside absorber

inside absorber

Photon Beam Exit Channel

A Closer Look…

22

X-Rays

Injected Beam

X-Rays

Stored Beam

NORMAL

X-Rays

Injected Beam

X-Rays

Stored Beam

Injected Beam

ACCIDENT

Stored Beam

X-Rays

Injected Beam

X-Rays

Injected Beam

Ratchet

WallFixed

Mask

Top-Up with Safety Shutters Open

SAFE

23

X-Rays

Injected Beam

X-Rays

Stored Beam

Injected BeamACCIDENT

•Bad steering, energy

Experimental

Floor

Simulation is necessary!

Is this a real possibility?

•Bad magnet fields

Shield

Wall

QF QD BEND SDINSERTION DEVICE

A1 A2

Stored Beam on

design orbit

Ratchet

WallFixed

Mask I

Fixed

Mask IIComb

Mask 9.1

CM

SPEAR3 Magnets BeamlineIncoming Beam

•No assumptions

about initial steering

•All physical

positions and angles

possible

•Energy errors!

•No magnetic field

•Straight trajectories

Beamline Apertures

Vacuum Chamber

Radiation Masks

Safe

Endpoint

Start

Point

Field simulation region

SSRL Approach to Calculations

• Wide fringe fields

A.Terebilo

25

A1 Aperture

A2 Aperture

Fixed Mask

Stored Beam

Injected Beam

Ratchet Wall

(2-ft Concrete)

Forward Propagation Only

Chamber boundary

26

-3 -2.5 -2 -1.5 -1 -0.5 0-0.24

-0.22

-0.2

-0.18

-0.16

-0.14

-0.12

-0.1

-0.08

X [m]

X' [r

ad]

Phase Space at Z = Fixed Mask

Phase Space at Z = Ratchet Wall

Fixed Mask Opening

Ratchet Wall Opening

Horizontal Position (m)

Horizonta

l Angle

(ra

d)

vacuum chamber acceptance fixed mask

10 bendo

spread in angles

(far fringe field)

Trajectories in Phase Space

27

-0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.1-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

X [m]

X' [r

ad]

Initial: A1 and BPM7

After BPM1

-0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.1 0.12-0.04

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

0.04

0.05

X [m]

X' [r

ad]

BPM1

After QF

A2

Dipole Entrance

-0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2-0.04

-0.02

0

0.02

0.04

0.06

0.08

0.1

X [m]

X' [r

ad]

Dipole Entrance

Dipole Exit

SD Exit

-3 -2.5 -2 -1.5 -1 -0.5 0-0.24

-0.22

-0.2

-0.18

-0.16

-0.14

-0.12

-0.1

-0.08Allowed Phase Space in BL coordinates

X [m]

X' [r

ad]

Z = SD exit

Z = Fixed Mask

Z = Ratchet Wall

QF QD BEND SDInsertion Device HCOR

A1 A2

Stored Beam on design orbit

X-Rays to Beamline

Ratchet

WallFixed

Mask I

BPM 7 BPM 1

Evolution of allowed phase space

28

-3 -2.5 -2 -1.5 -1 -0.5 0-0.24

-0.22

-0.2

-0.18

-0.16

-0.14

-0.12

-0.1

-0.08

X [m]

X' [r

ad]

Phase Space at Z = Fixed Mask

Phase Space at Z = Ratchet Wall

Fixed Mask Opening

Ratchet Wall Opening

The Metric: Separation in Phase Space to Apertures

29

A1

QF QD BEND SD

ID A2BPM 7 BPM 1

Stored Beam

on design orbit

Beamline Axis

Extreme Ray

4 6 8 10 12 14 16-1.4

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

Z [m]

BL a

pert

ure

s a

nd E

xtr

em

e R

ay p

ositio

n [

m]

Beamline apertures and the most severely mis-steered beam

BL4

BL5

BL6

BL7

BL9

BL10

BL11

mis-steered beam

Extreme Ray

All other

Trajectories

The Extreme Ray

Position along beam line [m]

rise/run ~ -0.1 rad

ratchet wall

Offset [

m]

Separation at

Fixed Mask

beam pipe w/apertures

30

Large SPEAR3 magnet field error

- and/or -

Large injected beam energy error

- AND -

“extensive intentional steering”

Condition for ‘Abnormal’ Scenario

special SLAC interpretation

4 6 8 10 12 14 16-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

Z[m] from ID center

BL a

pert

ure

and E

xtr

em

e R

ay p

ositio

n [

m]

BL5

BL6

BL7

BL9

BL10

BL11

Nominal

B/B = -10%

B/B = -50%

B/B = -60%

Parameter To Pass Beyond Fixed

Mask

To Pass Beyond

Ratchet Wall

Target Value for

Interlock Limit

EINJ/ESPEAR +59% +100% +10%

B/B -48% -60% -1% (-10%)

QF -100% Only with polarity

reversed

-25%

QD +300% 55% (PS Limit)

HCOR 22 mrad 30 mrad 3mrad (2 x PS Limit)

Parameter Sensitivity

QF QD BEND SDInsertion Device HCOR

A1 A2 A3

Stored Beam on design orbit

X-Rays to Beamline

Ratchet Wall

PM

+60 / -43 mm +50 / -43 mm BL9: +112 / -101 mm

SPEAR

Apertures

Beamline-Specific

Aperture

Alignment of Apertures is Critical

33

Fixed

Mask

ID sourceRing

Aperture

Experimental Floor

xxx

Mechanical Drawings & Tolerances

Documentation

Periodic checks

More documentation

Dose Calculations & Testing

Bauer & Liu

mis-steer and measure…

35

Passive Systems

-Limiting apertures in transport line (BTS)

-Limiting apertures in SPEAR3 and beam lines

- Permanent magnets for dipole beam lines

Active Systems (Redundant Interlocks)

- Injection energy interlock

- BTS dipole supply

- SPEAR3 magnet supplies

- Stored beam interlock

- Radiation detectors at each beam line

‘Hazard Mitigation’

Hardware Interlock Envelope

Software Alarm Envelope

A

B

* *

path 1

path 2

Software Monitor Envelope

Interlock Hierarchy

(reportable incident)

A Rastafarian Logic Table

Corbett & Schmerge

1. Load operational lattice

- software check of PS readbacks

2. Inject to <20 mA (orbit interlock)

3. Start orbit feedback (few microns)

4. Inject to 50 mA – top-off permit

5. Open beam line injection stoppers

6. Fill 500 mA maximum (FOFB runs continuous)

7. Fill-on-fill or trickle charge

SPEAR3 Operating Sequence