1. EMMA Design and Construction
Bruno Muratori
STFC, Daresbury Laboratory
21/01/09

2. 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)

3. INJECTION LINE ALICE to EMMA
Vacuum valve
Tomography Section
Screens x 3
(emittance measurement)
SRS Quadrupoles x 3
Emittance measurement
Screen
Wall Current Monitor
SRS Quadrupoles x 2
Vacuum valve
Current
measurement
Screen
Screen &
Vert. Slit
EMMA
Ring
Beam Direction
BPM
Position
measurement
New Dipole 30°
& BPMs at dipole entrance
Position measurement
New Quadrupoles x 13
Match the probe beam to the requirements of EMMA
Measure the properties of the probe beam
Ion Pump
New Dipoles x 2 (33°)
& BPMs at dipole entrance
Position measurement

4. Diagnostics – injection line
OTR Screen in ALICE before extraction dipole
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

5. ALICE to EMMA injection line (2)
Tomography
diagnostics also used
to better control
beam
All matches achieved to
good accuracy – wyaiwyg
‘what you ask is what you get’
Different match for all
energies (10-20 MeV)
Twiss parameters and
dispersion and its derivative
are different for every energy
and have to be precise

6. EMMA Ring IOT Racks (3) Waveguide distribution Injection Septum 65°
Kicker
Kicker
Septum
Power
Supply
Wire Scanner
Wall
Current
Monitor
Kicker
Power
Supplies
Cavities
x 19
Extraction
Septum 70°
Screen
Kicker
Screen
Kicker
Septum
Power
Supply
D Quadrupole x 42
F Quadrupole x 42
Kicker
Power
Supplies
Wire Scanner
BPM x 82
16 Vertical
Correctors

7. 6 CELL Girder Assembly Location for diagnostics F Magnet Cavity
D Magnet
Ion
Pump
Girder
Beam direction

8. 2 Cell Section (standard vacuum chamber)
per 2 cells
Bellows
Field clamp plates
BPM
2 per cell
Beam direction
Vertical
Corrector QD QF
Cavity
Location for diagnostic screen and
vacuum pumping

9. Injection & Extraction (1)
Screen
Septum
Cavity
Cavity
Kicker
Kicker
Injection scheme shown
Extraction is Kicker, Kicker, Septum arrangement
Injection

10. 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

11. EMMA Kicker Magnet Fast Switching
Kicker Magnet Power Supply parameters are directly
affected by the compact design and require:
Fast rise / fall times 35 nS
Rapid changes in current 50kA/S
Constraints on Pre and Post Pulses
Magnet length
0.1m
Field at 10MeV (Injection)
0.035T
Field at 20MeV (Extraction)
0.07T
Magnet Inductance
0.25H
Lead Inductance
0.16H
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
Applied Pulse Power Collaboration
Design and construction of thyristor prototype units using magnetic switching and Pulse Forming Network techniques

12. Injection and Extraction
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
133 mm
internal
100 mm
25°
180 mm
Final Parameters

13. Septum Concept Electrical feedthroughs Translation & rotation
(conductor path to power supply requires to be short to reduce inductance)
Translation & rotation
in-vacuum bearings
0 - 7°
Motorised
linear actuators
external to vacuum
-7 to 15 mm
Vacuum flange
Aluminium wire seal
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.

14. 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
Section view of septum in vacuum chamber
ISO view of septum with vacuum chamber removed
Plan view of septum in vacuum chamber

15. Cavity Design Normal conducting single cell re-entrant
110 mm
Cavity machined form
3 pieces and EB welded at 2 locations
Parameter
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
Input coupling loop
Coolant channels
Aperture Ø 40 mm
Probe
EVAC Flange
Capacitive post
tuner
Normal conducting single cell re-entrant
cavity design optimised for high shunt impedance

16. Diagnostics / Extraction line
spectrometer dipole
ALICE
SRS quadrupoles
EMMA
New quadrupoles
TD Cavity

17. NEW DIAGNOSTICS BEAMLINE LAYOUT
Spectrometer
dipole entrance
Screen
Faraday Cup
Extracted momentum
Screen x 3
Tomography
Section
SRS Quadrupoles x 6
New Quadrupoles x 4
Emittance measurement
Screen
& Vert. Slit
Wall Current Monitor
E-O Monitor
Current measurement
Longitudinal profile
BPM &
Valve
Location for Transverse Deflecting Cavity
(NOT IN BUDGET)
Screen
ALICE
New Dipoles (43°)
& BPMs at dipole entrance
Position measurement
New Quadrupoles x 4

18. Diagnostic line
deflecting cavity
tomography EO
spectrometer

19. 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

20. TDC Resolution (1) σz L
deflecting voltage
deflector
bunch
screen z
In absence of quadrupoles resolution increases with distance (L) from TDC to screen

21. TDC Resolution (2) σz
deflecting voltage
deflector
bunch
screen z
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

22. Transverse deflecting cavity (1)
Transfer Matrix to screen gives
βd – deflector, βs – screen
Want R12 big → sinΔψ = 1, βs fixed → make βd large
Transverse displacement on screen is
Beam size on the screen

23. Transverse deflecting cavity (2)
tomography EO
spectrometer
0.95
1.35
1.6
Δµx = 90°
Δµy = 65°
1.13

24. 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 ≥ 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

25. 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

26. Milestones
ALICE shutdown (Cable management installation) 25 Oct – 21 Nov month
Diamond drilling of ALICE wall, cable tray installation
Off line build of modules Oct 2008 – Jun months
ALICE shutdown 1st Mar – 12th Apr wks
ALICE shutdown 8th Jun – 13th Jul wks
Installation in Accelerator Hall Mar – Aug months
Test systems in Accelerator Hall May - Oct months
Injection line and ring complete 31st Oct 09
Commission with electrons starting Nov 2009

27. 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

28. Acknowledgements
All the EMMA team
Internal staff
Collaborators