Christoph Gabor, ASTeC HIPPI—Meeting (WP 5) 26 th – 28 th September 2007 Non—destructive...

Christoph Gabor, ASTeC HIPPI—Meeting (WP 5) 26 th – 28th September 2007

Non—destructive transverseemittance measurement device

The Front End Test Stand Collaboration

C. Gabor, J. Pozimski, A. Letchford

Christoph Gabor, UKNF—Meeting, 3rd October 2007

Outline

Introduction FETS, Photo detachment & basic principle of beam diagnostic

Theoretical investigations

Proof of principle experiment Demonstration experiment at a small H- beam line in Frankfurt

Further Hardware

Summary & Outlook


Layout of the Front End Test Stand FETS

(PD) Diagnostic & Support

Beamstop

IonSource

(PD) Emittance Measurement

3 Solenoids90

sect

or

ma

gne

t LEBT RFQ324 MHz3 MeV

MEBTDiagnosticQuads,

Buncher,Chopper

3MeV beam energy, ~ 60mA H-

50Hz, <2ms (10% duty cycle)

at David Lee andJuergen Pozimski,Imperial College


Photo Detachment H— beam diagnostic

• non destructive (i.e. no mechanical parts inside the ion beam) => minimizing the influence on the H- beam (on line) highly suitable for high power applications like FETS

• different applications possible: profile(s), emittance ~ electrons, neutrals, laser power attentuation ~ more information about beam are possible, also with good resolution ~ separating neutrals and H- can cause less flexibility because of dipole ~ higher costs compared with a traditional emittance scanner

T hresho ld :=1644nm (0 ,754eV )

M A X : =840nm (1 ,476eV )

Photon energy /a.u. (atomic unit)

0

0,1

0,2

0,3

0,4

0,5

0 0,1 0,2 0,3 0,4

Cro

ss s

ecti

on

/a

.u.

Ine

last

ic r

eg

ion

:>

0,4

a.u

. (1

0,8

...1

4,4

eV

)

- -

-

-

--

-

LASER

Photodetachm ent

Chargeseparation

Magneticdipole

I(t)1dim profile,

long. emi

I(x,y,t)2dim profile,

trans. em i

Detection ofdistribution

y

z


Non-destructive, transverse H- emittance measurement

H -beam,Neutral atoms produced in the transport section

-

Laser, 1060 nm

H-b

eam

-

Neutra l a tom s produced in the transport section

M agnet poletips

B X

xy

z

Region of interactionand separation of thebeam s

scan

Scintillator

Comparission with a slit—slit emittance instrument:1st slit is replaced by a laser2nd slit is replaced by a scintillator with CCD camera more information (than 2dim) about phase space

Only a small portion of H- will be neutralized,

i.e. max. portion oflaser interaction


Different emittance measurement principles

Envellope ofthe ion beam

Cross section of the ion beam

sligh tly convergent ion beam envelope

A ngle m easurem ent p laneP osition m easurem ent p lane

"slit--s lit"p rincip le

"po in t--point"princip le

F irst step S econd step

R

R

z

x x

y y

drift length L

P (x ,y )0 0

L(y )0

(y ,y ')0

r= ( x, y)

y

( ,x ',y ')0x ,y0

Slit—slit Principle : only 2dim phase space = 2dim (y,y')Point—point Principle : full 4dim information about phase space


Photo detachment simulations aboutits transfer function

100

50

-50

-100-20 10-10 20

<PDsimK.dat>

y/mm

y'/m

rad

=0,138 mmmrad100%,rms,n

255075100

-60-40

-2020

040

60Angl

e [mrad]

y= -10mmy= +10mm

Intensity [a.u.]

-15-10-5051015

-10 0 10

x-axis /mm

y-axis

/mm

x

y-20

Left, beam profile I(y') integrated of the emittance pattern and integration of drifted, (100mm) neutralized particles (dots). Right, the "neutralized particles" at +/-10mm and the drifted particles, enclosed by the neutralized patterns, are shown.

beam profile phase space neutralized particles,drifted particles


Comparision of simulation & measurement

y/m m 10-10

100

50

-50

-100

y'/m

rad

-15 0 15

-20

500m m

20

500m m

50

-50

prf101.spe

prf139.spe

X

Y’

y=-3

,8m

my=

+8,

4mm

2dim yy‘ emittance simulation close to

the experiment

expe

rimen

tal r

esul

ts a

t di

ffer

ent

lase

r po

sitio

ns

simulation of photo neutralized ions of the xy distribution

(drift length 500mm


Further, current development work

Photodetachment Diagnostic Dipole (FETS)

D:\FETS\MAGNET\POISSON-SIMULATIONEN\H-MAGNET\UEBUNG@UNI\VERS-E_YOKE+COIL VARIATION\DIPOLE016.AM 2-12-2007 18:55:56

-10

0

10

20

30

40

50

60

-10

0

10

20

30

40

50

60

-20 -10 0 10 20 30 40 50 60 70 80 90

good field region20cm

4cm15cm

vacu

umve

sse

l

space for piezo driven stages

arc lenght: 500 mmdeflection angle: 60 degB—field: 0.522 T

I(y)

y

yx

1/e 2H beam-

m in angle

m ax angle

scanningregion

laser beam (reference) path

• homogeneity (waist) along the H- ion beam (collimation/ focusing)• different angles within scanning region

Limiting spatial resolution


Summary

-- Introduction about Photo detachment ion beam diagnostics Motivation; different principles of diagnostic using photo detachment; Comparison with other emittance measurement methods

-- Theoretical aspects investigations about transfer function of "slit—point" emittance

-- Proof of principle experiment in Frankfurt, Germany

Outlook and recent workFurther hardware:

diagnostic dipole & laser equipmenttesting laser beam line/ movable mirrorsparticle detector (beam test of scintillators like P43, 45improving theoretical understanding

Longitudinal emittance measurement


Spare slides


Piezoelectric motors: status

Motion controller

Rotary stage

Amplifiers and

power supplies

Linear stage

Encoders


Motivation for non-destructive diagnostics

665keV H-

1...3% dc30....40mA500 W/cm2

(by Alan Letchford)

Water cooled end plate of a Fast Faraday Cup

(unfocused ion beam)

Measurements at the current ISIS RFQ

Scintillator image of H- ion beamafter the ion source

=> beam not cylindrically symmetric mainly caused the slit extraction of the ion source

xy intensity distribution of H-,35keV 45mA,

(Ion source test stand)


Some data about Front End Test Stand FETS


Integration of a photo neutralized& drifted H- distribution

01

00

20

03

00

400

50

0

Pix

el

<=

> y

' /m

rad

In te nsity I(y ') /a .u . prf129.spe

y=+4,7mm

CCD image (raw data) + P43 with Alu

y

xRelationship between y, y and y'

y


Laser characterisation, beam guiding

Laser lab at Imperial college

Power meter

Attenuation

CCD camera

Switching mirror

Christoph Gabor, ASTeC HIPPI—Meeting (WP 5) 26 th – 28 th September 2007 Non—destructive...

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Transcript of Christoph Gabor, ASTeC HIPPI—Meeting (WP 5) 26 th – 28 th September 2007 Non—destructive...