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Denis Anielski 02.04.2009 1
Detector systems to find HFS of 209Bi80+ @ ESR
Emission characteristics Counting rates at existing mirror section Straight on detector option Parabolic mirror system Outlook
Denis Anielski, Volker Hannen, Raphael Jöhren, Christian Weinheimer
Westfälische Wilhelms-Universität Münster02.04.2009
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Denis Anielski 02.04.2009 2
• Relativistic Doppler Effect
λ = λ´γ(1- βcos(θ)) θ= 0° → 640nmλ´ = 1555nm θ= 40° → 1000nm
• Observed angle
• Boost
Relativistic Doppler Effect and Boost (β = 0.71)
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Denis Anielski 02.04.2009 3
Simulation of Boost
Polar angles in the comoving system Polar angles in the lab system(Isotropic light source)
A(0°,10°) = 4%A(10°;30°) = 25%A(10°;50°) = 52%
→ Most photons not in straight forward direction, because of sin(θ) in solid angle!
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Denis Anielski 02.04.2009 4
Ideas For Detector Systems
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Denis Anielski 02.04.2009 5
General Assumptions
Number of excited ions: 2 e5 Lifetime in lab system: 82 ms [1]
Lifetime in comoving system: 116 ms QE = 10% Circumference of ESR: 108 m β = 0.71
[1] V. M. Shabaev, PHYSICAL REVIEW A, JAN 1998
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Denis Anielski 02.04.2009 6
Mirror System
• 10 elliptical mirrors on a 65cm section• Original simulation software not
available• First order estimate: geometric count
rate estimate• Realistic simulations using GEANT4
under progress
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Denis Anielski 02.04.2009 7
Estimated counting rate
Counting rate is proportional to
Emitted photons per second NPh = N/tau = 1,72 e6
Ratio of totally emitted photons A = 0.38 (646 nm – 950 nm; 5°-37° )
Loss by reflexion and transmission R*T = 1/3 (R=0.35!!!)
Quantum efficency QE = 0,1
Relevant beam section b = 0.065m/ 108m
Geometry of mirror system g = 2/3
Number of windows (dia: 7cm) # = 3
→ f = NPh · A · g · RT · QE · b · # = 26 Hz
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Denis Anielski 02.04.2009 8
Straight on option
• Diameter of window: 60mm• Straight beam section: 17 m• Distance – beam – detector: 3,5 m• All Photons are focused on detector by a lense• Transmission of lense: 0.9
→ 0,36 Hz (simulation c++)
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Denis Anielski 02.04.2009 9
Parabolic mirror
Detects forward emission
→ short wavelengths
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Denis Anielski 02.04.2009 10
Parabolic mirror
Assumptions
• Reflectivity coefficient: 0.8
• Hole in mirror with diameter of 2cm for the beam
www.edmundoptics.comGEANT4 model
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Denis Anielski 02.04.2009 11
2-flange option
• Diameter of flange for mirror: 10 cm
• Diameter of flange for detector: 3.8 cm
• Distance: Beam - Detektor: 30 cm
• Straight section before mirror: 5 m
• Radius of mirror: 5 cm
• Lightguide as interface from window to detector
• GEANT4 simulation (Volker Hannen)
→ 15 Hz
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Denis Anielski 02.04.2009 12
2-flange option
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Denis Anielski 02.04.2009 13
1-flange option – C++ Simulation
• Diameter of flange: 20 cm
• Distance: Beam - Detektor: 25 cm
• Straight section before mirror: 5 m / 10 m
• Radius of mirror: 7.5 cm
• Radius of detector/ focussing system: 3 cm
• Counting rate is multiplied by 0.9 because of slit
→ 45 Hz / 60 Hz
(Flange is just in front of mirror system!)
Possible improvement with recessed exit window (distance beam – exit window = 15cm): 154 Hz
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Denis Anielski 02.04.2009 14
CPM beam tests
• Two setups have been installed at ESR yesterday
• Investigations of background photons and behaviour of CPM next to dipole magnet
• Positions:– 2-flange option– Straight on option
• Detectors: Channel-Photomultiplier– Easy to handle – Low dark count rate– Only 2% QE around 650nm – Suitable for 244nm transition at SPECTRAP
(QE= 18%)
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Denis Anielski 02.04.2009 15
Conclusions
Mirror system:
26 Hz, but dark counts of three detectors, broad wavelength range Reflexion of mirror? Not all three windows present ???
Straight on
very low rate ( < 1Hz) ???
Parabolic mirror
System with highest counting rate on a SINGLE detector Small wavelengths (640 – 680nm) !!!
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Denis Anielski 02.04.2009 16
Outlook
• Test of Hamamatsu R943-02 PMT(suitable detector for parabolic mirror system)
• Detailed GEANT4 simulation of existing mirror system and search for best parameters of parabolic mirror system