Multi-colour sctintillator-based ion beam profiler

James Green, Oliver Ettlinger, David Neely(CLF / STFC)

2nd Ion diagnostic workshopJune 7-8th

Talk outline

• Diagnostic outline

• Multi-channel characterisation

• Reducing EMP & radiation effects

• Demonstration on Astra Gemini

• Future developments

High-repetition rate advances

• Passive media (CR-39, RCF, Image plate) increasing unsuitable

• Transition to active diagnostics:Scintillators, Micro-channel plates (MCPs), Phosphor screens

Target

LaserCCD

Fibre bundle

Scintillators

Lens

Ion beam

Micro-channel plates (MCP)

Radiochromic film (RCF)

2D detector head development

• Diagnostic aims:– 2D beam profiling– Spectral measurement– Beam pointing– Calorimetry

• Compact scintillator beam head– Scintillator thickness determines

energy observation window– Each scintillator has a separate

central emission wavelength– Need to avoid optical excitation

within scintillator stackSc

intil

lato

r 3 (B

lue)

Scin

tilla

tor 1

(Ora

nge

Scin

tilla

tor 2

(Gre

en)

Incident Protons

100 mm 90 mm

Detector head

Proton stopping ranges

Optical Stimulation

• Optical Stimulation:– Emission from Blue or Green scintillators can optically

stimulate emission from scintillators earlier in the stack

– How to stop light travelling back through the system?

5

Scin

tilla

tor 3

(Blu

e)

Scin

tilla

tor 1

(Ora

nge

Scin

tilla

tor 2

(Gre

en)

Incident Protons

Reducing EMP / radiation impact

• High resolution 800 x 800 fibre bundles– Image relay from Phosphor / Scintillator to camera

outside interaction chamber– Durable with flexible deployment options– Wide transmission range– Long fibre lengths (> 5 m) possible

• Eliminating background radiation– Gated CCDs to block X-ray / electron signal– CCD safely shielded from hard hits

60um

60um

Core

OpticalCladding

OpticalCore

Groups of fibres inside bundle

Channel separation

• Signal split in front of camera into 4 channels, RGB + Extra

• Dichroic filters used to isolate each scintillator signal

RedGreen

Blue All channelsData obtained using from SRIM – http://www.SRIM.org

Data Deconvolution

• System characterised using a Cyclotron proton source

• Produced a response matrix for each colour channel

8

Predicted Response Matrix - Ideally require 1 on the diagonal,

with 0 everywhere else

Astra Gemini experiment• Astra Gemini –

– 12J 50fs– 5x1020 Wcm-2

– >1010 contrast– TCC – Scintillator = 20 cm Sc

intil

lato

r 3 (B

lue)

Scin

tilla

tor 1

(Ora

nge

Scin

tilla

tor 2

(Gre

en)

Incident Protons

1 - 4.5 MeV7-9 MeV

10.5 - 14 MeV

Laser

Astra Gemini experiment

1- 4.5 MeV 7-9 MeV 10.5-14 MeV

0 100 200 300 400 500 600 700 800 900 10000

20

40

60

80

100

120

Target thickness (nm)

Mea

n CC

D co

unts

50 nm Al

• Shot a range of Al foils, 25-900 nm• Clear signals on orange and green

channels, insufficient flux for blue• Clear structure visible with peak off

axis for some shots

FOV = 30o

100 nm Al

Imaging novel targetry

• Microspoke targets shot on Astra Gemini

• Proton beam imaged using RCF and Scintillator stack

11

1mm

Disks: 32um diameter, 40nm thick SiN membranes

Supporting wires: 1µm wide , 40 nm thick

Hole etched through 400μm thick Si.

Scintillator

RCF

10 Hz operation

• Scintillator considerations:– Rapid (s) recovery between shots– Minimising high dose damage

• Implement new Scientific CMOS camera– 30 fps continuous full-frame operation– Low noise read-out, 16-bit Dynamic range

• Data analysis– Real-time data deconvolution for live beam

profiles (Desirable – looking for collaborators?)

Future developments

• Further diagnostic testing– 0.05 Hz to 10 Hz progression– Efficient data capture and analysis

• Scintillator development– Thin scintillators for high spectral resolution– Calibration at higher (> 30 MeV energies)– Faster scintillators for fast gating– Media lifetime

• Experimental & industrial collaborations– Experimental access on range of facilities– Next-gen imaging and scintillator technology