w. bayer – abi workshop, bad kreuznachemittance measurements at gsi unilac11. dez. 2008 emittance...

11. Dez. 2008 W. Bayer – ABI Workshop, Bad Kreuznach Emittance measurements at GSI UNILAC

Emittance Measurement at GSI UNILACEmittance Measurement at GSI UNILAC

– Results and Requirements –– Results and Requirements –

W. Bayer, W. Barth, L. Dahl, P. Forck L. Groening, S. Yaramyshev

P. Gerhard, M. Maier

– ABI Workshop –

Bad Kreuznach, 11.12.2008


OverviewOverview

Motivation

GSI UNILAC – Parameters and beam diagnostics

Procedures for Experiments

Results of UNILAC measurements

– at 1.0 emA 40Ar10+ at DTL entry


Conclusion


Note about FAIR (Note about FAIR (FFacility for acility for AAntiproton an ntiproton an IIon on RResearch)esearch)

Important data:

Z = -1, 1 … 92intensity of secundary radioactive ion beam : up to 10 000 times moreintensity of primary beam :

100 to 1000 times moreenergy: 35 to 45 GeV/u…


Design parameters and requirements for FAIRDesign parameters and requirements for FAIR

Present 90% trans. emittances of 15 emA 238U28+ at 11.4 MeV/u due to DYNAMION* simulations:

x = 1.1 mm mrad

y = 3.6 mm mrad

UNILAC upgrade program until 2009 one aim: increase of high intensity beam brilliance

* S. Yaramyshev et al., NIM A 558 (2006) 90


HIPPI Project OverviewHIPPI Project Overview

CARE: Integrating Activity within FP6Coordinated Accelerator R&D in Europe2004 – 2008, i.e. 5 years

HIPPI: Joint Research Activity within CARE High Intensity Pulsed Proton Injector

Total GSI cost: 1476 k€, provided by EU to GSI: 363 k€

GSI – Activities:

Beam dynamics code development & benchmarkingBeam dynamics experiment campaign (1 week in May/November 2006, resp.)Beam diagnostics development

Thanks to HIPPI the accelerator division acts for the first time as experimentalist at GSI


MeasurementsMeasurements

Required: better understanding of correlation between space charge forces and focusing during acceleration

Within HIPPI: experiments & simulations ( code benchmarking by A. Franchi)

For Benchmarking: experiments without & with space charge forces

Alvarez quadrupoles yet are not sufficient to provide for the required phase advances for high current 238U28+ beam

(part of upgrade program)

As space charge force

7.1 emA 40Ar10+ instead of 15 emA 238U28+ for experiments

Ion

Ion ~A

IZ


OverviewOverview

Motivation






Conclusion


Overview ofOverview of GSI GSI UNIUNIversal versal LLinear inear ACACceleratorcelerator

High Current Injector (HSI)

Alvarez Single Gap Resonators


Parameters of UNILAC Alvarez DTLParameters of UNILAC Alvarez DTL

5 independent rf-tanks + 2 re-bunchers

108 MHz, 50 Hz, 5 ms

192 rf-cells

DTL based on F-D-D-F focusing

dc-quads grouped to 13 families

Inter-tank focusing : D-F-D

Transv. acceptance (norm.) = 15 m

Synchr. rf-phases -(30°,30°,30°,25°,25°)

Ekin [MeV/u]:

Tank :

A1 A2a A4A2b

1.4 3.6 4.8 5.9 8.6 11.454 m

Re-BuncherA3


Overview of Beam Diagnostics EquipmentsOverview of Beam Diagnostics Equipments

Stripper & matching section with selected beam diagnostics

transverse emittances

Beam diagnostic devices:

longitudinal emittance

phase probe

beam current transformer

beam profile grid


Longitudinal Bunch Structure & Emittance before DTLLongitudinal Bunch Structure & Emittance before DTL

TOF measurement with Multi Channel Plate & diamond detector in relation to rf timing;

Methode suited especially for low ion beam energies;

Very sensitive methode (view ions per rf-periode sufficient).


Longitudinal Emittance in TKLongitudinal Emittance in TK

Sketch by P. Gerhard

Beam behinddispersive section

Rhombaperature

dEdt

"Pencil" like beam from core of main beam

Verticalchopper

Luminescent screen& CCD camera

Slit Grid

Online measurement


OverviewOverview

Motivation






Conclusion


High Current Matching of the Alvarez DTLHigh Current Matching of the Alvarez DTL

Measurement of transverseTwiss parameters and rms-emittances

Measurement of the longitudinal Twiss parameters and rms-emittance

Calculation of 6 Twiss parameters and 3 emittances at entrance of 1st re-buncher regarding the settings of the doublet, the 1st re-buncher and the measured emittances as input parameters for matching routine

Variation of quadrupol strengths and re-buncher amplitudes to match the periodic solution at DTL entrance; routine based on rms envelope tracking of space charge affected beams (*)

Measurements of transverse emittances behind DTL before & after applying calculated settings to verify improvement

(*) see T. Wangler, Principles of RF Linear Acc., p. 217 & 287


Example of DTL MatchingExample of DTL Matching

40Ar10+, 9.5 emA, 1.4 MeV/u

vertical

horizontal

after manual matching

meas. transmission = 93%

after systematic matching

meas. transmission = 96%

matching quads


Evaluation of Measured Phase Space Distributions with ProEMIEvaluation of Measured Phase Space Distributions with ProEMI

Level Mode Level Mode

Level Mode Intensity Mode

Amplifier noise like a carpet

Cut noise at certain level (normally < 2%)

Remove remaining pixels that obviously do not belong to beam signals

Evaluate with intensity mode


OverviewOverview


Motivation

Matching of the Alvarez DTL




Most recent results

Conclusion


Results of HIPPI I: Long. Emittance Results of HIPPI I: Long. Emittance BeforeBefore DTL DTL

Before optimisation: After optimisation:

40Ar13+ (1emA 40Ar10+) pstripper = 480 mbar

DW/W ≈ ±2.5%, j ≈ ±160° (core)j ≈ ±430° (with satellite)

40Ar10+ (1emA 40Ar10+), pstripper = 2000 mbar

DW/W ≈ ±2.0%, j ≈ ±120°

Design values: DW/W = ±0.5%, j = ±90°

Normalised emittances

for f = 108 MHz

Normalised emittances

for f = 108 MHz

(1 emA 40Ar10+)


Results of HIPPI I: Trans. Emittance Results of HIPPI I: Trans. Emittance BeforeBefore DTL DTL


(1 emA 40Ar10+)


Results of HIPPI I: Trans. Emittance Results of HIPPI I: Trans. Emittance AfterAfter DTL DTL


(1 emA 40Ar10+)


Summary of These ResultsSummary of These Results

Longitudinal Emittance Before DTL:tot,90 = 34.1 mm mrad

tot,90 = 20.3 mm mrad

Transverse Emittance before DTL:x,tot,90 = 0.63 mm mrad, = 2.3, = 1.3 mm/mrad

y,tot,90 = 0.64 mm mrad, = 1.6, = 1.9 mm/mrad

x,tot,90 = 0.69 mm mrad, = -0.3, = 12.4 mm/mrad

y,tot,90 = 0.62 mm mrad, = 2.2, = 3.8 mm/mrad

Transverse Emittance after DTL:x,tot,90 = 1.61 mm mrad emi. growth: 2.56

y,tot,90 = 1.63 mm mrad emi. growth: 2.55

x,tot,90 = 0.88 mm mrad emi. growth: 1.28

y,tot,90 = 0.68 mm mrad emi. growth: 1.10

blue: before optimisationred : after optimisation

(1 emA 40Ar10+)


Results of HIPPI I: Beam Energy & EmittanceResults of HIPPI I: Beam Energy & Emittance

Main transverse emittance growth took place in tank A1Possible reason: still remaining mismatch of tank A1

(1 emA 40Ar10+)


Results of HIPPI I: Alvarez BuncherResults of HIPPI I: Alvarez Buncher

Alvarez Bunchers „Off“Alvarez Bunchers „On“

1st buncher focusing2nd buncher defocusing

(1 emA 40Ar10+)


OverviewOverview


Motivation

Matching of the Alvarez DTL




Most recent results

Conclusion


Longitudinal Emittance Before Alvarez DTLLongitudinal Emittance Before Alvarez DTL

Contrary to HIPPI I two intensity centres in the longitudinal phase space appearance of double peak structure not yet fully understood

Only weak correlation, i. e. -1 < < 1

All DTL matching routines were based on the measurement

calculated new quadrupole strength & adapted buncher amplitudes reduced emittance growth

Design

(7.1 emA 40Ar10+)


Investigations on Long. Emittance Measurement (in 2007)Investigations on Long. Emittance Measurement (in 2007)

Measurement of energy spread & phase width reliable but correlation, i. e. too small

Setup-Changes in 2007:

new Ta-foil due to damages (no double peak?)improved DAQre-alignment of the setup

40Ar7+, stripped, IH2 off

influence on correlation?

40Ar4+, unstripped, IH2 off

(7.1 emA 40Ar10+)


Measurement of Measurement of ((00) – Procedure) – Procedure

Procedure:

– Changing all phase advance quadrupoles to the desired 0;

– Calculation of the re-buncher, doublet & triplet settings with the matching routine;

– Changing doublet & triplet settings to calculated values, adapted buncher settings.

(7.1 emA 40Ar10+)


Examples of phase space distributions for different Examples of phase space distributions for different 00 after after DTLDTL

0 = 35° 0 = 60° 0 = 90°0 = 45°









Transverse emittances at DTL entry: x,tot,90 = 0.57 mm rad, y,tot,90 = 0.92 mm mrad

(All emittance values are normalised ones!)

(7.1 emA 40Ar10+)


Measurement of Measurement of ((00) – Procedure & Reproducibility) – Procedure & Reproducibility

Procedure:

– Changing all phase advance quadrupoles to the desired 0;

– Calculation of the re-buncher, doublet & triplet settings with the matching routine;

– Changing doublet & triplet settings to calculated values, adapted buncher settings.

Reproducibility: values remeasured after finishing the complete scan.

(7.1 emA 40Ar10+)


Results of Results of 00 Variation Variation

Simulations with Parmila & Dynamion were & are performed

(7.1 emA 40Ar10+)


Transverse Emittance Growths at Transverse Emittance Growths at 00 = 60° (7.1 emA = 60° (7.1 emA 4040ArAr10+10+))

Horizontal emittance growth: 3.33

Vertical emittance growth: 1.69





(Zero current)


Summary & OutlookSummary & Outlook

Overview of beam diagnostics mounted at GSI UNILAC

Measurement principles of longitudinal emittance

Procedures of experiments & data processing

Results of measurements at low & high 40Ar10+ beam intensities:– Low int.: (E) emittance growths for 0 = 45°: 1.28/ 1.10;

– High int.: (0) minimal trans. emittances at 60°: 1.74/ 1.79 mm mrad;

– High int.: (E) emittance growths for 0 = 60°: 1.69/ 3.33.

Investigations on the longitudinal emittance measurement before DTL:– Improvements of new installed DAQ

– Investigations of new detectors to improve time resolution

– Answer the question „Why results measurement in 0“

Longitudinal emittance measurements in transfere channel to SIS18– Installation of new DAQ for fluorescence screen observation

– Quantification of emittance value of slit-grid measurement


Appendix


MotivationMotivation

Presented at previous HIPPI Meetings:– Results of low current beam (space charge forces neglectable)

experiments at GSI UNILAC;

– Results of corresponding simulations with the DYNAMION code;

Results fit to each other.

2 truncated Gaussian distribution(DYNAMION generated distribution for given Twiss parameters)


Energy ParasitesEnergy Parasites

Beam fractions ( 10%) with lower energy emittance growthcaused by

longitudinal mismatch at the transition from 36 to 108 MHz rf section

beam energy spread and phase width exceed designvalues

longitudinal mismatchbetween DTL sections

inhomogenous density profile of gas stripper jet

Measured beam profiles in dispersive section:





Data aquired under different conditions as in (0) measurements!

w. bayer – abi workshop, bad kreuznachemittance measurements at gsi unilac11. dez. 2008 emittance...

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