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Transcript of Mitglied der Helmholtz-Gemeinschaft Josefine Metzkes [email protected] [email protected]...
Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
Scintillator-based online detectors for laser-accelerated protons
–Concepts and realizations
at the DRACO lab
J. Metzkes, K. Zeil, S.D. Kraft, N. Stiller, U. Schramm, L. Karsch, C. Richter,
J. Pawelke, M. Sobiella
Instrumentation for Diagnostics and Control of Laser-Accelerated Proton
(Ion) Beams II
June 7 – 8, 2012
Seite 2 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
The DRACO laser facility
time [fs]
30 fs
-80 -40 0 40 80
Ti:SapphireCPA laserrep rate: 10 Hz2-3 J (on target)I ~1021 W/cm2
ns-ASE contrast 10-10
*Dre
sden
lase
r ac
cele
ratio
n so
urce
Seite 3 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
Proton acceleration at DRACO
RCF @ wheel2Doffline
target changer
targetmanipulation
Thomson parabolasmall solid angleonline
online laser parameter control
Seite 4 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
Proton acceleration at DRACO
RCF @ wheel2Doffline
target changer
targetmanipulation
Thomson parabolasmall solid angleonline
online laser parameter control
Status
stable high repetition rate laser system reliable proton source
high degree of remote control under vacuum
online optimization and monitoring of acceleration performance
application experiments
online spectrometers for protons & ions (1D or 2D)
NE
ED
Seite 5 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
Why plastic scintillators?
Mainly practical reasons:
easy to handle
available in nearly any size and thickness no support necessary
immediate light emission after excitation online information
variable emission wavelength in the visible range
signal readout with CCD cameras less EMP issues
fast decay rates possible TOF applications
linear response to particle flux
light emission saturates with dE/dx calibration
light emission degrades with total dose exposition
Seite 6 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
Detector setup1D angularly resolved online spectrometer for protons
•scintillator stack: 10 layers of BC 418 (Saint-Gobain crystals), maximum emission @ 391 nm
•resolution of 10 proton energy ranges
•light guide principle slim scintillator unit (15 mm x 76 mm)
•fan-like setup for good spatial resolution
•detection area: 10 mm x 50 mm detection angle as for RCF (~ 26° half angle )
• compact detector: scintillator and camera unit only 300 mm x 80 mm
•radiation shielding with Pb
Seite 7 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
Detector setup
camera:
◦ 16 bit camera high dynamic range
◦ 1600 x 1200 px chip size, 4.4 µm pixel size
camera unit directly coupled to the scintillator:
◦ light tight connection stray light suppression
◦ high light yield
◦ good spatial resolution 7px per layer thickness
Seite 8 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
Imaging properties
edges roughened to avoid reflection
imaging edge polished
spatial resolution
surfaces polished for efficient reflection
182 mm
8.6 mm
Seite 9 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
Detector setup & proof of principle
proton distribution reconstructed from RCF
p+
ener
gy
Measured proton distribution
CCD camera image
Seite 10 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
Detector setup & proof of principle
p+
ener
gy
Measured proton distribution
CCD camera image
sufficient signal-to-noise ratio (>2) for signal detection shielding against electron and x-ray background
maximum proton energy and yield online accessible for the full divergence angle of the proton beam
online detection of beam inhomogeneities improves online beam optimization
Seite 11 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
Detector characterization @ Tandetron
6 MV tandetron at the HZDR Ion Beam Center
12 MeV p+ beam
FC – 25.4 mm diam. detection surface current ~ 100pA
detector
reference RCF – beam homogeneity
beam defining aperture – 10 mm diam.
reference RCF – beam position
Seite 12 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
Sensitivity calibration
Seite 13 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
Sensitivity calibration
dE/dx saturation of scintillator light output
light transport within the scintillator case correction possible
condition of polished scintillator edge
Seite 14 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
Lateral homogeneity
lateral position
decrease due to imaging properties
• overall lateral homogeneity: ~ 80%
• inhomogeneity due to scintillator conditions stable
measured curves give correction factors
Seite 15 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
Imaging properties testing
spatial resolution imaging properties
Seite 16 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
Imaging properties testing
spatial resolution imaging properties
Seite 17 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
Detector application
Idocis
aper
ture
beam
filte
r
aper
ture
targ
et
laser
on
lin
e d
etec
tor
proton beam
Phys. Med. Biol. 56 (2011) 1529–1543
non-invasive online access to spectral distribution and yield of accelerated protons
Seite 18 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
Detector application
optimal focus 25 µm out of focus
dispersion
ener
gy
online optimization & monitoring of experimental performance via maximum proton energy & yield
shot-to-shot monitoring via yield (higher sensitivity)
online spectral monitoring dosimetry
Seite 19 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
2D online detector development
profile A-A`
profile B-B`
profile C-C`
2,5
0,4
0,7
1,0
1,9
2,1
2,5
1,2
1,4 1,6
Idea: mimic an RCF stack 2D spectrum ONLINE
~ 50
~ 5
0
4,5
4,5
A A`
B B`
C C`
Schnitt A-A`
Schnitt B-B`
Schnitt C-C`
2,5
0,4
0,7
1,0
1,9
2,1
2,5
1,2
1,4 1,6
CCD camera
scin
till
ato
r
Seite 20 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
2D online detector development
~ 50
~ 5
0
4,5
4,5
A A`
B B`
C C`
cam
era
un
it
absorber matrix & scintillator (BC 416, thickness 260 µm)
Detector setup
Seite 21 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
2D detector testing
test with 12 MeV p+
basic pixel (9 energies): 4.5 x 4.5 mm 121 pixels on a 50 x 50 mm plate
diam 1.5 mmdist 2.0 mm diam 1.5 mm
dist 2.25 mm
diam 1.5 mmdist 2.50 mm
diam 1.5 mmdist 2.75 mm
diam 1.0 mmdist 1.50 mm
Test matrix optimized for tandetronexperiment (12 MeV protons)
Seite 22 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
2D detector testing
basic pixel (9 energies): 4.5 x 4.5 mm 121 pixels on a 50 x 50 mm plate
Progress
final design for basic pixel
sensitivity calibration @ tandetron
test of p+ scattering in angled holes
To do
• test of a final design @ DRACO
performance with background radiation
Seite 23 Mitglied der Helmholtz-GemeinschaftJosefine Metzkes [email protected] www.hzdr.de HZDR
(multiple filamentation of a freely propagating 100 TW beam in air)
… thanks for your attention