proton detection in the spectrometer
TRANSCRIPT
Proton Detection in the Spectrometer aSPECT
M. Simson1,4, H. Angerer1, F. Ayala-Guardia2, S. Baeßler2, M. Borg2, J. Byrne3, K. Eberhardt2, F. Glück2, M. van der Grinten3, W. Heil2, I. Konorov1, G. Konrad2, R. Munoz-Horta2, G. Petzoldt1, Y. Sobolev2, H.-F. Wirth1, O. Zimmer1,4
1 TU München2 Johannes-Gutenberg-Universität Mainz
3 University of Sussex4ILL Grenoble
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Outline
• The “old” Detector– Setup– Performance during the
beam times– Systematic investigations
• A new Detector– Detection principle– First results with a test
detector– Outlook: The “new”
detector• Conclusion
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Detector & Preamplifier(~ -30 kV)
Digital electronics
UHV-gate valve
ExB electrodes
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The aSPECT Detector
• Si-PIN Diode– 25 Strips – Strip size 0.8 x 25 mm2
– Entrance Window 67 nm (40 nm Si3N4 + 27 nm SiO2)
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Readout Electronics
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Pulseheight Spectra
Pulseheight Spectra for 50 V and 800 V at the analyzing plane
Background (800 V) subtracted spectra
Detector at 30 kV
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Offline Data Analysis
Fit of the events with theoretical known pulse function
Single proton events: High noise, low signal: background-ratio (~10:1)!Bad separation of proton- and background-peak in the pulse height spectrum
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Diode Characteristics
Det. 2: Does not detect protons any more
Det. 4: Still detecting protons
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Proton Source
Specs:– Proton energy 10-35 keV– Flux: nA to several CPS– Two monitor detectors– Other ions possible
paff: “proton accelerator with femto ampere flux“
Detector
A.R. Müller et al. submitted to NIM A
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Between the Strips
Gap between the strips: 200 µm Small, movable aperture ( Ø 0.2 mm) before the detector
Submitted to NIM A
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Temperature effects
Cooling the setup reduces the amount of noise significantly
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A new detector type
• New Type: Silicon Drift Detector (SDD)• Principle:
p-doped backsidep-doped rings
P. Lechner et. al. , XRS 2004 33 256-261
Potential Valley
e- drift to a smallanode in the middle
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SDD Test Detector
• Supplied by HLL / PNSensor• Features:
– Active area: 30 mm2
– Integrated FET– Mounted ready to use
– Mounted on a Peltierelement
– Optimized preamp + shaper
– Integrated temperature diode
– Different entrance windows available
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First Spectra with the SDD
First protons on the SDD:
Detector at room temperature
Submitted to NIM A
Energy Calibration with a 55Fe source:
Mn-Kα − FWHM @ -13 °C:~ 165 eV
Submitted to NIM A
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First Spectra with the SDD II
Comparison:
protons – electronic noise
Protons on the cooled detector:
Impact energy 12 keV
Temperature -4 °C
Submitted to NIM A
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Charge Collection Efficiency
• 3 part function• 4 Parameters
– S : Minimum (starting point)
– τ : Steepness
– c : Shape
– l : Depth
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Simulations done with SRIM
Simulations
Questions:How much energy is detected for each proton?
How many protons are backscattered?Is there an angular / energy dependence?
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Artificially broaden thesimulation by the noise
S = 0.41τ = 75 nmc = 2l = 50 nm
Tune the CCE parametersto fit the measurements
From Measurement to CCE
EXYZ-File Calculate ΔEfor each line
Multiply itby the CCE
Integrate over thecomplete track
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A new detector for aSPECT
active area: 3 x 100 mm²14
mm
34 mm
Temperature diode
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A new detector for aSPECT II
• Advantages:– Noise performance comparable to the test
detector– HV only ~ 15 kV– New (simplified) detector mechanics– Simplified preamplifier (based on 3 Amptek A250)
• Disadvantages:– Loss of spatial resolution– (Slightly) reduced count rate
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Conclusion
• First beam times with aSPECT completed
• Present detector performance not satisfying
• New SDD detector successfully tested• SDDs will be ready for the next beam time at
the ILL in autumn
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Online Trigger
• No external trigger self-triggering system• Signals are shifted through time bins• Trigger settings:
– W1: Long window(baseline): 512 bins
– W2: Short Window(event): 16 bins
– Threshold: 15 ADC-Channels
– Delay: 3
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Magnetic shield
High magnetic field might disturb other experiments
-> magnetic shield:– 4 poles 0.2x0.2x4 m– 2 plates 1.8x1.8x0.1 m– ~10 t iron
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Coupling Constants of the Weak Interaction
dn = (ddu)
p = (udu)u
W±
e-
νegV, gA
Coupling Constants in Neutron Decay
W±
e-
νen
p
n + νe → p + e-
Nucleosynthesis
W±
e+
νe
n
p
n + e+ → p + νe
Solar cycle
W±
e+
νe
p + p
2H+
p + p→ 2H+ + e+ + νe
W±
e-
νe
p + p
2H+
p + e- + p → 2H+ + νe
Neutrino Detection (SNO, CC)
W±
νe
e-
2H+
p + p
νe + 2H+→ p + p + e-
n → p + e- + νe
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Standard Model Test
Cabibbo-Kobayashi-Maskawa-Matrix
Condition of Unitarity
• Superallowed Fermi Decays
• Neutron Decay
• Pion Decay
• Kaon Decays
• Hyperons
• B/D Mesons
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-1.28-1.27-1.26-1.25λ = gA/gV
0.965
0.970
0.975
0.980V ud
τn [PDG2006]A [PERKEO II]
0+→ 0+
ud u2
u2
s b1V V V= − +Unitarityof the CKM Matrix
Neutron Measurements needed:
• Neutron lifetime τn
• Beta Asymmetry A(λ)
• Neutrino-Electron-Correlation a(λ)
( )21 2n ud
2 1 3FVGτ λ− ∝ +
2
2
Re2
1 3A
λ λλ
+= −
+
2
2
11 3
aλλ
−=
+
Vus [Blucher et al., CKM 2005]
τn [Serebrov 05]
A [PERKEO II]
Situation 2004New Ke3 and Kμ2 measurementsNew Neutron Lifetime Measurement
[Marciano, Sirlin, 2005]; λ = gA/gV
uV
udA F
dFFermi-Transition: Gamow-Teller-Transition:
g Gg
VG V
= ⋅= ⋅ ⋅λ
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Determination of λ
PERKEO II, 1997
PERKEO II, 2002
Yerozolimskii, 1997
PERKEO, 1986
Liaud, 1997
Serebrov 05
Unitarity,PDG2006
Unitarity,
Unitarity,PDG2004
Stratowa, 1978
Byrne, 2002
-1,285
-1,275
-1,265
-1,255λ
• Different Systematics Measurement of a is independent of possible errors in A
• An accuracy of Δa/a < 1% is needed !
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Information in the Proton Spectrum
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The spectrometer aSPECT
SPECTrometer for a
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Properties of the Detector
• Diode IV characteristics• Detection performance
– Different impact angles– Different proton energies– Gaps between the strips
• Temperature effects
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Diode Characteristics
Det. 2: Does not see protons any more
Det. 4: Still seeing protons