Published on July 27, 2011
Janusz HarasimowiczDaresbury, 13 July 2011Project Update Low Energy, Low Intensity Beam Diagnostics
Ultra-low Energy Storage RingUSR @ FAIRFacility for Antiproton and Ion Research
Challenges Intensity Current range: µA → fA Close to noise limitations (fA) No standard UHV components for low current measurements Position Low signal: ~1 µV @ 0.1 mm Noise level: >2.5 µV @ 20 MHz BW Low velocity: 0.025 c → 0.006 c Profile Low energy: <300 keV Low intensity: ~106 pps (sub-pA) Particles: antiprotons AND protons
Noise Sources E-M interference (shielding) Triboelectricity C Parasitic (low-noise cables) capacitance Ground loops (triaxial cables) Faraday Beam Contamination Cup (cleaning) Leakage current (guarding) HV Ammeter Charge escape Supply (repelling electrode) Electrostatic coupling (low ripple, rigidity)
Signal Cable Inner shield Outer shield Triaxial cableCurrent Ground Ammetersource loop In-house built UHV triaxial solution for ultra-low currents measurements
Amplifiers Slow Slow Fast extraction extraction extraction (DLPCA-200) (DLPCA-200) (LCA-2-10T) 1012 Gain 106 107 1011 1013 2 HzUpper 1.1 kHz 500 kHz 400 kHz 0.3 Hzcut-off (10 Hz) 0.1 Hz 0.2 sRise/fall 0.7 µs 0.9 µs 300 µs 1s time 5s Input 1.8 450 0.18 fA/√Hz 4.3 fA/√Hz noise pA/√Hz fA/√Hz @ 0.2 Hz Max 10 pA (1012) 10 µA 1 µA 100 pAinput I 1 pA (1013)
Experimental Setup Floating feedthrough Faraday cup vesselElectron gun
Initial results with electrons
Initial results with electrons I = (V – V0) / G G [V/A] = 1012 ± 2% I = 97.7 fA ± 2.3 fA
Initial results with electrons I = (V – V0) / G G [V/A] = 1012 ± 2% I = 14.6 fA ± 0.9 fA
End of Part 1Annihilation! Fast pionsAntiproton Recoiling nuclear fragments …
Signal Estimation Estimate: ΣU ≈ 600 Vp-p ∆U ≈ 1 µVp-p / 0.1 mm ×46 dB: ΣU ≈ 120 mV ∆U ≈ 200 µV / 0.1 mm
End of Part 2Labview Application
Secondary Emission Monitor Mesh MCP + goes phosphor here over here Foil back there
Principle of Operation (Thin) foil Mesh Beam MCP Secondary electrons Phosphor up to -10 kV +2 kV approx. +5 kV
Protons 200 keV p 50 keV p 5 mm 50 mm 20 keV p 3 mm 6 mm MCP/phosphor Foil Mesh (0V, +2 kV, +5 kV) (-10 kV) (0 V) Primary beamAdditional shielding needed
H– (same conditions) 50 keV H– 20 keV H– 200 keV H– Primary beamAdditional shielding needed
Experiment @ MSL, Stockholm Al plate: –6.4 kV MCP: +1.2 kV Phosphor: +2.0 kV Collimator Al Mesh MCP1 MCP2plate Grounded metal ring Fluorescent screen
Experiment @ MSL, Stockholm Charged particles Bremsstrahlung photons? F.S. = fluorescent screen
Shielded SEM Entrance mesh FoilExit mesh(if needed)
2-in-1 SEM Foil + MCP MCP alone
Black electrons 10 eV Green electrons 5 eV Red electrons 1 eV Blue electrons 0.1 eV foil -5 kVSecondary electrons emitted in 60 deg half angle (120 deg)
Black electrons 10 eV Green electrons 5 eV Red electrons 1 eV Blue electrons 0.1 eV foil -7.5 kVSecondary electrons emitted in 60 deg half angle (120 deg)
Black electrons 10 eV Green electrons 5 eV Red electrons 1 eV Blue electrons 0.1 eV foil -10 kVSecondary electrons emitted in 60 deg half angle (120 deg)
End of Part 3Annihilation!
Thank you for your attention
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