h- low energy emittance measurements to optimize injections into an rfq christoph gabor

[email protected]/ Spain, Ditanet Diagnostics Conf., 2011 slide 1

H- Low Energy Emittance measurements to Optimize

Injections into an RFQ

Christoph GaborASTeC(south),

Rutherford Appleton Laboratory


Companies:Tekniker, Jema, Elyt

Diversified TechnologyToshiba

Further collaboration:CERN

IHEP, ChinaFermilab

IAP, Frankfurt University

Dan FairclothSimon JollyScott Lawrie

David LeeAlan Letchford

Jürgen PozimskiPeter Savage

Christoph GaborMark Whitehead

Trevor WoodsGary BoormanAlessio Bosco

Mike PerkinsJohn BackAjit Kurup

Ciprian PlostinarMike Clarke-Gayther

Phil WiseJavier Bermejo

Julio LucasJesus Alonso

Rafael EnparantzaGrahame BlairZunbeltz IzaolaIbon Bustinduy

The Front End Test Stand Collaboration


Outline of the talk

Details of the Low Energy Beam Transport (LEBT), diagnostics hardware, i.e. emittance scanner

Front End Test Stand FETS at RALOverview of the project

Experimental results anddiscussion of measurements

(PD) Diagnostic & Support

Beamstop

IonSource

(PD) Emittance Measurement

3 Solenoids90

sect

or

ma

gn

et LEBT RFQ324 MHz3 MeV

MEBTDiagnosticQuads,

Buncher,Chopper

Fron

t slit

of t

he IS

IS

emitt

ance

sca

nner

, wat

er-

cool

ed, p

ower

dep

ositi

on

up to

600

W p

ossi

ble


The main components of the beamline are.....

65 keV, 60 mA, 2 ms, 50 Hz, H– Ion Source

3 Solenoid Magnetic LEBT

324 MHz, 3 MeV, 4 Vane RFQ

MEBT and Beam Chopper

Beam Diagnostics and Beam DumpThe LEBT transforms the

the divergent into a convergent beam tomatch the acceptanceof the RFQ.

In high power applications typical problems are high space charge forces and (large) divergence angles.


Beam travels through sector magnet, post acceleration and solenoid LEBT.

Isolating Column

1×10-4 mBar

6×10-5 mBar

Beam shutter

Slit-slit scanners

5×10-6 mBar

Retractable Faraday Cup

2000 Ls-1 Turbo Pump

Pepper pot or profile scintillator

head

Camera7×10-6 mBar

Solenoid 3

Toroid3

Solenoid 2

Solenoid 1

Toroid 1

Toroid 2

4 × 800 Ls-1 & 1 x 400 Ls-1 Turbo Pumps

Differential pumping and laser

profile vessel

400 Ls-1 turbo pump

Diagnostics vessel

Toroid 4


Laser

Diagnostics Vessel

3 Solenoid LEBT

Ion Source

[email protected]/ Spain, Ditanet Diagnostics Conf., 2011

Design now complete for the 4m long, 3MeV, 324MHz 4—vane RFQ

horizontal, vertical

x, yx’, y’

+/- 2mm+/- 100mrad

rms

0.25 mmmrad 0.840.032 mm/mrad

Sections made of 2 major and 2 minor vanes

3D o-ring


Two independent slit—slit scanner are installed in a multipurpose diagnostics vessel.

0.25 x 60 mm position

sampling slit

0.08 x 60 mm slit and

Faraday cup

500 V Electron Suppressor

Scan in one plane with resolution used for this work ~13min1mrad, 0.25mm: Mechanical resolution is enhanced by oversampling (Lucy—Richardson Deconvolution)For data processing, bias, threshold and SCUBeX can be applied.

(for more information see M.P. Stockli et al., AIP Conf. Proc. 639, pp135 2002)


17keV 20keV 35keV 40keV 60keV

17keV 20keV 35keV 40keV 60keV

ho

rizo

nta

lv

ert

ica

l

v/ h006 1-0075_2 01108 09

0

10

20

30

40

50

60

1 2 3 4

Toroid No. 1...4Bea

mC

urre

nt/m

A17keV 20keV

30keV 40keV

50keV 60keV

35 45 55 65

unnormalized emittance100% emittance

based on SCUBeX algor ithm

Beam energy /keV20

40

60

80

100

120

15 25

rms,

SC

UB

eX e

mitt

an

ce /

m

mm

rad

possible exaggeration due to truncated beam

Solenoids were set to same field,

equivalent to 70A.

verticalhorizontal

B [T] ~1.4*10-3*I

[I / Ampere]

Variation of the beam energy with constant extraction voltage of 17kV.


Constant beam energy of 65keV at different solenoid settings and beam currents up to 60mA.

S =137A, S =0A, S =0A

1

2 3

S =137A, S =0A, S =100A

1

2 3

S =137A, S =100A, S =100A

1

2 3

S =137A, S =100A, S =150A

1

2 3

S =137A, S =123A, S =216A

1

2 3

vert

ica

lh

ori

zon

tal

147...156_20110817

y = -30.....+60mm

y =

-8

0..

...+

80

mra

d

x = -60.....+30mm

100%,norm (SCUBeX)=0.502 mm mrad

100%,norm(SCUBeX)=0.594 mmmrad


100%,norm(SCUBeX)=0.546 mm mrad


100%,norm(SCUBeX)=0.459 mmmrad






Fractional rms—emittance versus different post acceleration gap lengths & extraction system.

Green: PA=13mm (v)Red: PA=6mm (v)Blue: PA=13mm (v)Solenoids off:Black: PA=13mm (V)dash: PA=13mm (h)

Definition of fractional rms-emittance

• Calculate sum of 100 of all pixel-intensities • Sort intensities from top by their contents• Sum them up until the fraction p% from 100

is reached• Use the pixels included in this sum for the rms—emittance.

0.01

0.10

1.00

10.0

100

0 0.2 0.4 0.6 0.8

Inte

ns

ity

10

0-%

norm / m m m rad

horizontal, all off, PA=13m m

focussing,PA=13m m

focussing,PA=6m m ve

rtic

al

0.01

0.10

1.00

10.0

100

0 0.1 0.2 0.3 0.4 0.5 0.6

Inte

ns

ity

10

0-%

norm / m m m rad

vertical em ittances

extr

act

jaw

1.1m

m w

ide

extract jaw2.1m m wide

S1=115A, S2=0A, S3=70A

40keV40keV


Summary and Outlook.

Horizontal 0.49 πmm.mRad (rms norm.)

Vertical 0.29

πmm.mRad (rms norm.)

The most urgent problem to solve is the misaligned beam in both transverse planes.Displacement depends heavily on solenoid/ PA settings and is not easily to correct with implemented steerer magnets.


Thank you for your attention

Questions, Comments?


Sector magnet, post acceleration and LEBT with dimensions in long./ radial direction.


The PA influences the beam with its lens effect, measured with a scintillator at z~1st solenoid.

The effective focusing depends on current and chosen beam energy, assuming that the gap is constant. It is difficult to estimate the best compromise for both transverse planes.

h- low energy emittance measurements to optimize injections into an rfq christoph gabor

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