Commissioning EMMA

transcript

Bruno Muratori

STFC, Daresbury Laboratory

Commissioning EMMA

02/07/09PRISM workshop – Imperial College

Motivation / Introduction

• Give an overview of what has been thought about – given talks & previous attempts (Scott, Eberhard, Shane, Carol, François, Dejan and others)

• Does not mean it is always correct or complete – this is part of our duty in the next months

• May be different & much better ways of implementing procedures – these are initial thoughts

• Requires several iterations & discussions• Process started & lots to think about• Aim to be ready by end of summer (~ October)• Need help – who is available & for what ?

Overview

• Commissioning– Preparing machine for beam

• set-up DAQ & controls & hardware• set-up diagnostic devices required

– Getting beam into the machine & where you want it– Making sure all desired properties are achieved

• for the bunch (full characterisation etc.)• for the machine (e.g. dispersion-free sections)

– Making all the desired measurements– Set-up machine for particular experiments– Requires several fully consistent simulations of the

machine !

ALICE schematic

SOL-01

H&V-01

H&V-06BPM-01

BUNCHERYAG-01

SOL-02

H&V-02 BPM-02

YAG-02 Q-02

BPM-03

H&V-03 Q-03

YAG-03

DIP-01

DIP-02

YAG-??

FCUP-01

BPM-04H&V-04

Q-06Q-07

Q-08Q-09

YAG-04

Q-11 BPM-05H&V-05

INJECTOR

OTR-01BPM-01H&V-01

OTR-02 DIP-01DIP-02

DIP-03Q-01

OTR-03

BPM-02H&V-02

Q-02 Q-03 Q-04

OTR-04

BPM-01DIP-01

BPM-02SEXT-01

OTR-01

ST1 ARC1

BPM-03

DIP-02

BPM-04

OTR-02SEXT-02

BPM-05DIP-03

BPM-06

OTR-01

Q-01Q-02

BPM-01H&V-01

OTR-02

Q-03Q-04

BPM-02H&V-02DIP-01

DIP-02BPM-03V-03

OTR-03

DIP-03

DIP-04Q-05

ST 2ST 2

ARC 2 PLM-01TCM-01

BPM-04H&V-04

BPM-05H&V-05

BPM-01H&V-01

Q-06Q-07

WIGGLER

ST 3ST 3

Q-01Q-02

Q-03Q-04

OTR-01

BPM-02H&V-02

BPM-01DIP-01

BPM-02SEXT-01

OTR-01

BPM-03DIP-02

BPM-03Q-03

OTR-02SEXT-02BPM-05

DIP-03BPM-06

OTR-01Q-01 Q-02

BPM-01H&V-01

DUMP-01

Q-04 Q-05

BPM-02H&V-02

OTR-02DIP-01 DIP-02 DIP-03

BPM-01Q-01

Q-02Q-03

OTR-01

Note: scale is for guidance only

ERLP SCHEMATIC DIAGRAM

v.0.2 (15/06/2006)extracted from AO-180/10078/E

• Need similar schematic for EMMA injection line, ring and extraction line (shall be enormously more detailed … !)

Injection Line (1)

ALICE quadrupoles

SRS quadrupoles

New quadrupoles

Faraday Cup

Screen

last dispersivesection

dogleg

tomography

Injection line (2)

Injection Line (3)

Injection Line Commissioning (1)

• Prepare ALICE as Injector for EMMA– Bunch length: ~ 10 ps rms in order to decrease space

charge effects and for painting the longitudinal phase space

– Energy spread: < 100 keV in order to have a better defined beam for painting and avoid chromaticity

– Bunch charge: 15 – 30 pC in order to reduce collective effects (e.g space charge)

– Normalised transverse emittance: 5 - 10 µm in order to decrease space charge effects but still have a well defined beam for painting

– Beam energy: 10 to 20 MeV with the ability to be changed several times a day.

– Beam characterisation (full 6D)• Bunch length / Charge / Emittance / Energy /

Energy spread– Hardware commissioning– Controls & online model commissioning

• Which is best suited ?– DAS commissioning

• Probable sequence of ALICE set up to act as an injector for EMMA– Set the ALICE injector up for an appropriate booster

beam energy (6 – 8 MeV) at 1 – 2 bunch charges (15 – 30 pC) too low / too high ?

– Characterise the beam in the ALICE injector for energy spread, emittance and bunch length etc.

– Set 3-4 injection energies in the range 10 to 20 MeV and set the rest of ALICE for injection into the EMMA ring

– Measure the beam characteristics at each combination of energy and bunch charge

Detailed Procedures (1)

• Dogleg & dispersion– Iterative procedure setting two external quads – then

central – then repeat• Matching to tomography

– Not trivial & very sensitive even in initial tracking models• Last dispersive section and setting Dx & D’

– Tomography helps keep the beam small– Dedicated model with some quads off– Measure dispersion in two places → derivative known– Turn quads to nominal model value → Dx & D’

x should be close to desired value ... is this a valid procedure ?

Measurements in Injection Line (1)

• Emittance– Tomography section– Quadrupole scan

• Bunch length– Zero cross method with 2nd linac cavity used as a

buncher and YAG screen in dogleg• Charge

– Faraday cup after dipole or tomography• Energy & Energy spread

– Slit & YAG in last dispersive section

Commissioning the EMMA ring (1)

Injection Septum 65°Kicker

Kicker

Cavities x 19

Extraction Septum 70°

Kicker

KickerScreen

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

KickerPowerSupplies

SeptumPowerSupply

KickerPowerSupplies

Injection

Extraction

• Before Injection into EMMA– Start with easier energy (probably 17-18 MeV)– Start with a low charge ? (e.g. 1 pC)– Measure injection energy to within 100 keV– Set nominal septum & kicker values

• Inject beam & look at first few BPMs – no acceleration– Calibrate this w.r.t. chosen model (ZGOUBI)– Make half a turn & extract & diagnose beam (may be

better to circulate first & measure tunes & TOF ?)– Measure bunch properties in extraction line

Establishing the orbit (1)• Look at Beam Position Monitor (BPM) one by one from the

injection point (not symmetric → not straightforward)• Adjust initial beam position (x,x’,y,y’) as well as Quad

current and position

Establishing the orbit (2)

• Double focusing lattice (QF and QD)• Bend fields are created by shifting quadrupoles

Linear slide

• 4 knobs– QF and QD strength– QF and QD position

(horizontally)

• 4 parameters to fit

– Qx and Qy

– TOF shape and offset• Should have model to

predict 4 parameters according to desired lattice which model is best ?

Measurements in EMMA ring

• Measurement of time of flight– Change frequency until no synchrotron oscillations– Frequency then translates into TOF– Hence find minimum of TOF

• Relationship of TOF to lattice parameters / tune– Tune vs. energy

• Study variation of all parameters to lattice properties• Interpretation of BPM readings

– Not all identical & only symmetry every other cell– Important to model all BPM readings → GPT / other

• Best code to do this – ZGOUBI (more this p.m.)

SRS quadrupoles

New quadrupoles

TD Cavity

spectrometer dipole

tomography, EOand spectrometer matching section and TDC

first dispersive section

Diagnostic line (1)

Diagnostic line (2)

Diagnostic line (3)deflecting cavity tomography EO

spectrometer

Extraction Line Commissioning (1)

• Much harder than injection as no precise knowledge of energy

• Set kickers & septum at ‘best guess’• Extract ideal – pencil-like beam• Measure energy with screen & dipole• Iterate• Zero the dispersion on exit of 1st straight (not obvious)• ‘Match’ to tomography – not trivial & again possibility for

collaboration (already two students & me but ...)• Make bunch measurements

• How to achieve zero dispersion at the exit of straight ?– Usually done by centering the beam and then slightly

changing the energy & ensuring spot is motionless– Where do we introduce this change ?

• main linac → changes dynamics of EMMA & spot could appear still with dispersion non-zero

• switch off one of the EMMA cavities ? → also changes the dynamics

• slightly reduce all of them ?• look at centroid trajectories ?

Detailed Procedures (2)

Measurements in Extraction Line (1)

• Emittance– Tomography section

• Slice emittance– TDC & screen in tomography section

• Bunch length– EO monitor and / or TDC

• Charge– Faraday cup after spectrometer dipole

• Energy spread– Slit & YAG in first dispersive section / spec. dipole

• Slice energy spread– TDC & spectrometer dipole

Modelling (1)

• Model ALICE injector to deliver EMMA beam (10 ps etc.)• Create model of ALICE to EMMA injector line in GPT

– Run this model both on & off line for comparisons / predictions

• Create S2E model for all of EMMA in GPT– Run with field maps & misalignments for comparisons

/ predictions– Run all the way to spectrometer & dump in the EMMA

extraction line• Compare this with ZGOUBI models & FFEMMAG / other

models wherever possible

Aperture survey

• Phase space at injection• Scan aperture in phase space with a pencil beam• Use steerers vertically & kickers horizontally

• When is normalized acceptance is 3 mm rad ?• Explore acceptance at all energies• Should also be modelled with FFEMMAG, GPT & others• To be done at all energies from 10 to 20 MeV

pencil beam

Online Modelling (1)• Ring optics – what things may look like

courtesy S. Machida

Online Modelling (2)• Injection orbit and optics - what things may look like

Set septum and kicker strength

See orbit and optics of incoming beam

courtesy S. Machida

We Need Your Help

• Identify all tasks required to operate EMMA successfully - started

• Identify & describe procedures – started– TOF / Tunes / Orbit correction / Experiments / other ?

• Help prepare programme of work - started• Help develop online models where required - started• Help interpret data & measurements correctly – what

does everything mean ?• Begin to lay out a commissioning plan - started• Estimate resources available to the project and in

particular commissioning – started• I will send list of tasks & initial commissioning thoughts

• Update commissioning document to have– Project plan for EMMA commissioning preparation

• Deliverables / Milestones• Who can look into it, STFC, collaborators etc.• Simulations to be carried out (Richard D’Arcy &

others)• Procedure writing

• Give this plan to collaborators for feedback & help• Full Commissioning Plan by end of October• Major tasks e.g. - Build online model with interface

(ZGOUBI / PI-ZGOUBI)– Already under way thanks to Yoel Giboudot, David

Kelliher, Shinji, Machida, Kiril Marinov, Ben Shepher

We Need Your Help

Thanks you for your attention

Still lots of work to be done !

Expect requests for help soon ...

Pre-Commissioning Workshop ~mid November

Everyone invited

Commissioning EMMA

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