EMMA Design and Construction

Bruno Muratori

STFC, Daresbury Laboratory

21/01/09

The EMMA Project

• EMMA (Electron Machine with Many Applications) is a design for a non-scaling FFAG – the world’s first

• Collaboration of : BNL, CERN, CI, FNAL, JAI, LPSC Grenoble, STFC, TRIUMF

• Part of BASROC (British Accelerator Science and Radiation Oncology Consortium) / CONFORM (COnstruction of a Non-scaling FFAG for Oncology, Research and Medicine)

• Advantages:– Linear fixed field magnets: large dynamic aperture– Cheaper

• Disadvantages:– Novel longitudinal & transverse dynamics– Rapid tune variations: multiple resonance crossings

• Many potential applications– Driver for ADSR, µ acceleration, medical (e.g. PAMELA)

INJECTION LINE ALICE to EMMA

New Dipoles x 2 (33°) & BPMs at dipole entrancePosition measurement

New Dipole 30°& BPMs at dipole entrancePosition measurement

BPMPositionmeasurement

Wall Current Monitor

New Quadrupoles x 13

Ion Pump

Vacuum valve

Tomography SectionScreens x 3(emittance measurement)

SRS Quadrupoles x 3

Screen &Vert. Slit

Beam

Dire

ction

SRS Quadrupoles x 2

Screen

Vacuum valve

Screen

Emittance measurement

Current measurement

EMMARing

ALICE

• Match the probe beam to the requirements of EMMA

• Measure the properties of the probe beam

Diagnostics – injection line

• OTR Screen in ALICE before extraction dipole• BPMs @ entrance of every dipole in injection line• Straight ahead Faraday cup to measure charge & energy spread• OTR screen in dogleg for bunch length & energy measurement• Tomography section: 60 degrees phase advance per screen with

three screens for projected transverse emittance measurements and profiles

• Last dispersive section:– OTR screen & vertical slit in middle of first section together with– OTR screen in final section for energy and energy spread

measurements– Vertical steerers for position & angle before ring (to be used

with kickers for steering)– BPM at entrance of EMMA ring for position before entering

ALICE to EMMA injection line (2)

Tomographydiagnostics also usedto better controlbeam

Twiss parameters anddispersion and its derivativeare different for every energyand have to be precise

Different match for allenergies (10-20 MeV)

All matches achieved togood accuracy – wyaiwyg‘what you ask is what you get’

Injection Septum 65°

Kicker

Kicker

Cavities x 19

Extraction Septum 70°

Kicker

Kicker

Screen

Wire Scanner

Wall Current Monitor

Wire Scanner

Screen

BPM x 82

D Quadrupole x 42F Quadrupole x 42

16 Vertical Correctors

IOT Racks (3)

Waveguide distribution

EMMA Ring

KickerPowerSupplies

SeptumPowerSupply

SeptumPowerSupply

KickerPowerSupplies

6 CELL Girder Assembly

IonPump

CavityD Magnet

F Magnet Location for diagnostics

Beam direction

Girder

2 Cell Section (standard vacuum chamber)

Cavity

QD

QF

Vertical Corrector

BPM2 per cell Beam direction

BellowsStandard vacuum chamberper 2 cellsField clamp plates

Location for diagnostic screen andvacuum pumping

Injection & Extraction (1)

Kicker Kicker

Septum

CavityCavity

Injection

Screen

Injection scheme shownExtraction is Kicker, Kicker, Septum arrangement

Injection and Extraction (2)

• Have to match ‘orbits’ at all energy ranges & for all settings (10 – 20 MeV)

– Kickers

– Septum rotation & motion

– In-house code (FFEMMAG - Tzenov)

– Vertical & Horizontal steerers in injection line – also used for painting (3 mm rad acceptance)

• Kickers specified at 0.07 T

EMMA Kicker Magnet Fast Switching

Magnet length 0.1m

Field at 10MeV (Injection) 0.035T

Field at 20MeV (Extraction) 0.07T

Magnet Inductance 0.25H

Lead Inductance 0.16H

Peak Current at 10/20MeV 1.3kA

Peak Voltage at Magnet 14kV

Peak Voltage at Power Supply

23kV

Rise / Fall Time 35nS

Jitter pulse to pulse >2nS

Pulse Waveform Half Sinewave

Kicker Magnet Power Supply parameters are directlyaffected by the compact design and require:• Fast rise / fall times 35 nS• Rapid changes in current 50kA/S• Constraints on Pre and Post Pulses

Applied Pulse Power CollaborationDesign and construction of thyristor prototype units using magnetic switching and Pulse Forming Network techniques

Injection and Extraction

133 mm

internal

100 mm

25°

180 mm

internal

Final Parameters

• Large angle for injection (65°) and extraction (70°) very challenging !!

• Injection/Extraction scheme required for all energies 10 – 20 MeV, all lattices and all lattice configurations

• Minimise stray fields on circulating beam• Space very limited between quadrupole magnet

clamp plates

Septum Concept

Motorisedlinear actuatorsexternal to vacuum

Electrical feedthroughs (conductor path to power supply requires to be short to reduce inductance)

Vacuum flangeAluminium wire seal

Translation & rotationin-vacuum bearings

Conductor connections with flexibility to feedthrough to accommodate septum movement

Pole gap 25 mm• Complete septum assembly mounted from top section of vacuum chamber lid.• 2 linear actuators provide translation and rotation of septum.

-7 to 15 mm

0 - 7°

Septum Design

• In house design of septum and vacuum chamber in progress

• Wire eroding of lamination stacks scheduled for February, steel delivered.

• Magnet measurements scheduled for April 09

Plan view of septum in vacuum chamber

Section view of septum in vacuum chamber

ISO view of septum with vacuum chamber removed

Cavity Design

Normal conducting single cell re-entrant cavity design optimised for high shunt impedance

Capacitive post tuner

Probe

Coolant channels

Input coupling loop

EVAC Flange

Aperture Ø 40 mm

110 mmParameter Value

Frequency 1.3 GHz

Theoretical Shunt Impedance

2.3 M

Realistic Shunt Impedance (80%)

2 M

Qo (Theoretical) 23,000 (23000)

R/Q 100 Ω

Tuning Range -4 to +1.6 MHz

Accelerating Voltage 120 kV 180 kV

Total Power Required(Assuming 30% losses in distribution

90 kW 200 kW

Power required per cavity

3.6 kW 8.1 kW

Cavity machined form 3 pieces and EB welded at 2 locations

ALICE

EMMA

SRS quadrupoles

New quadrupoles

TD Cavity

spectrometer dipoleDiagnostics /

Extraction line

NEW DIAGNOSTICS BEAMLINE LAYOUTSpectrometer BPM @ dipole entranceScreenFaraday Cup

E-O Monitor

Screen x 3Tomography Section

Wall Current Monitor

BPM & Valve

SRS Quadrupoles x 6

New Quadrupoles x 4

ALICE

New Dipoles (43°) & BPMs at dipole entrance

Current measurement Longitudinal profile

Position measurement

New Quadrupoles x 4

Screen& Vert. Slit

Emittance measurement

Extracted momentum

Location for Transverse Deflecting Cavity(NOT IN BUDGET)

Screen

Diagnostic linedeflecting cavity tomography EO

spectrometer

Measurements

• Energy– First dipole & spectrometer at end with OTRs

• Projected transverse emittance– Quadrupole scans & tomography 60° phase advance / screen– Equivalent set-up in injection line for comparisons

• Bunch length– EO monitor downstream of the tomography section– No profile information

• Possibility of introducing a transverse deflecting cavity (TDC) to measure additional bunch properties

σz

L

0x

x

deflecting voltage

deflector bunch

screen

z

TDC Resolution (1)

• In absence of quadrupoles resolution increases with distance (L) from TDC to screen

σz

x

deflecting voltage

deflector bunch

screen

z

TDC Resolution (2)

• In the presence of interspersed quadrupoles this is not so and we must take into account of the entire transfer matrix from TDC to screen – there can be as many quadrupoles as desired

01 11 12''01 21 22

xx R R

xx R R

• Transverse displacement on screen is

• Beam size on the screen

• Transfer Matrix to screen gives

βd – deflector, βs – screen

• Want R12 big → sinΔψ = 1, βs fixed → make βd large

Transverse deflecting cavity (1)

Transverse deflecting cavity (2)

deflecting cavity tomography EO

spectrometer

0.95

1.35

1.6

Δµx = 90°

Δµy = 65°

1.13

Transverse deflecting cavity (3)

• Reverse of formula gives requirement of cavity voltage

• Take Δµ = 65° and φ = 0• For streaked bunch to be comparable to un-streaked bunch

• βx,y = 9 m at the deflecting cavity therefore we need, assuming an emmitance degradation to 10 µm and a bunch length of 4 ps

eV0 ≥ 0.23 MV @ 1.3 GHz

• Equality gives a streaked beam which is √2 times un-streaked beam– only rough idea of requirements– not enough for ≥ 10 slices (what we would like) → ~ 1 MV ?– longer bunch lengths / better emittance → lower voltage

20 0| sin cos |

N

z d

eV pcm c

Measurements with TDC

• Slice emittance & transverse profiles given by

– knowledge of R12 from TDC to screen

– one dimension on screen gives slice emittance– other dimension gives bunch length

• Slice energy spread given by– streaked beam and spectrometer

12 sind sR 01 11 12''01 21 22

xx R R

xx R R

Milestones

ALICE shutdown (Cable management installation) 25 Oct – 21 Nov 2008 1 monthDiamond drilling of ALICE wall, cable tray installation

Off line build of modules Oct 2008 – Jun 2009 9 months

ALICE shutdown 1st Mar – 12th Apr 2009 6 wks

ALICE shutdown 8th Jun – 13th Jul 2009 5 wks

Installation in Accelerator Hall Mar – Aug 2009 6 months

Test systems in Accelerator Hall May - Oct 2009 6 months

Injection line and ring complete 31st Oct 09

Commission with electrons starting Nov 2009

Conclusions

• All components of injector line ordered (most already at DL)• Order for Extraction / Diagnostic line to go out soon• Very Challenging & exciting project !• Good characterisation of the beam at injection & extraction even

without TDC• Have good location for TDC should it be used in the future

– Realistic voltage parameters– Extra beam properties not available with EO– Currently looking at requirements for TDC with RF engineers

• Aim to be commissioning with electrons at DL in November 2009• Aim to demonstrate that non scaling FFAG technology works and

compare results with the theoretical studies performed to gain real experience of operating such accelerators

Acknowledgements

• All the EMMA team

– Internal staff

– Collaborators