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LEIR Schottky system and Experimental Results J.TAN AB/BDI

LEIR Schottky system and Experimental Results J.TAN AB/BDI. Outline. LHC ion injector chain LEIR Machine Schottky Pick-Ups Commissioning with : Oxygen ions O 4+ Lead ions Pb 54+ Summary. LHC Filling Scheme : Pb 54+ ions. 200 e m A. Pb 27+. 27+. 82+. 54+. 54+. Pb. Pb.

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LEIR Schottky system and Experimental Results J.TAN AB/BDI

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  1. LEIR Schottky system and Experimental ResultsJ.TANAB/BDI Jocelyn TAN CERN AB / BI

  2. Outline • LHC ion injector chain • LEIR • Machine • Schottky Pick-Ups • Commissioning with : • Oxygen ions O4+ • Lead ions Pb54+ • Summary Jocelyn TAN CERN AB / BI

  3. LHC Filling Scheme : Pb54+ ions 200 emA Pb 27+ 27+ 82+ 54+ 54+ Pb Pb Pb Pb ECR 4.2 MeV/u, b=0.095 rep. rate 1 to 5Hz Energy ramping cavity Dp/p~0.4% LINAC3 RFQ LEIR • stacking of 9x108 ions at 4.2 MeV/u • accel. to 72 MeV/u • 2 bunches of 4.5x108 ions each • cycle length 3.6s 592 bunches ~ 10mn filling time per ring. 7.107 /bunch 2.76TeV/u, L = 1027 cm-2 s-1 LHC *accel. to 5.9 GeV/u *Double bunch splitting SPS *4 pairs of bunchlets per 3.6s PS ~13 PS inj./ SPS cycle 1 ej./1. mn at 177GeV/u Jocelyn TAN CERN AB / BI

  4. LEIR Machine (1) Nominal Lead Ions Cycle : 3.6s Extraction 1.2 B[ T ] 72 MeV/u 1.0 multi-turn injection 200ms 0.8 Main dipole field [T] 0.6 Electron cooling + Stacking Acceleration 0.4 0.2 4.2 MeV/u t[ms] 0.0 0 500 1000 1500 2000 2500 3000 3500 ejection injection • Injection repetition rate : 1 to 5 Hz • Beam unbunched for 1600ms • Schottky signals are essential for diagnostics and controlling phase-space cooling efficiency Jocelyn TAN CERN AB / BI

  5. LEIR Machine (2) extraction point injection line Electron cooler Jocelyn TAN CERN AB / BI

  6. Stripline electrode t2+t1 t2 t1 A B • Striplines electrodes • Z0 = 50 • Matched lines L picking up the signal upstream the line A B picking up the signal donwstream the line Jocelyn TAN CERN AB / BI

  7. LEIR : Travelling-Wave mode • Travelling-Wave Striplines for lowenergyparticles P ~ (Nstripxi0)2 delay delay 3i0 2i0 i0 Jocelyn TAN CERN AB / BI

  8. LEIR : Travelling-Wave mode delay delay • Travelling-Wave Striplines for lowenergy particles Beam delay delay Superposition of currents Good S/N ratio Hybrid S port D port Total power ~ (Nstripi0)2 Jocelyn TAN CERN AB / BI

  9. LEIR : Parallel combination • Monitor backward signal : for high (any) energy particles Hybrid Hybrid Hybrid i0 i0 i0 delay1 delay2 Combiner Total power ~ Nstripxi02 Jocelyn TAN CERN AB / BI

  10. Schottky Pick-Ups Layout UCV22-TW EXTRACTION : Parallel mode INJECTION : Travelling Wave mode Vertical : 8 pairs of stripline-electrodes Horizontal and Longitudinal : 24 pairs of stripline-electrodes Vertical : 6 pairs of stripline-electrodes Horizontal and Longitudinal : 24 pairs of stripline-electrodes Jocelyn TAN CERN AB / BI

  11. In the control room... 75 dB Pick-Up -45 -55 -65 -75 -85 -95 -105 Dp/p = 4.10-3 N=2.25x108 Lead ions -145 dBm/Hz -70 dBm/Hz noise level of the spectrum analyser = -140 dBm/Hz Inj. trigger 100th harmonic at 36 MHz reduced thermal noise = -177 dBm/Hz Resolution BW = 1.5 kHz Peak signal = - 38 dBm ( i.e. 2.7 mV peak) Aug. 2007 : new Spectrum analysers + remote desktop Jocelyn TAN CERN AB / BI

  12. Commissioning with O4+ ions : Oct.-Nov. 2005 • Expected longer vacuum life-time than with Lead ions (lower cross section for charge exchange processes with the residual gas) • O4+ and Pb54+ have very close Z/A Nearly same beam rigidity for both ion species • Results and observations • Unexpected shorter lifetime : vac. leaks + desorption • Fast losses coupled w/ transverse “activities” observed : coupling impedances ions trapped in potentials created by e- beam • Interpretation of beam cooling not straightforward • frev = 363.3 kHz • Injection momentum spread ~ 4x10-3 • Qh = 1.795 Qv = 2.604 Longitudinal plane Horizontal spectrum Vertical spectrum (100+qh ).f0 (50-qv ).f0 (50+qv ).f0 (101-qh ).f0 50.f0 99.f0100.f0101.f0 Jocelyn TAN CERN AB / BI

  13. Commissioning with Pb54+ ions : 2006-2007 : Nominal Scheme Spectrogram of the momentum cooling during stacking on the injection front porch. The vertical and horizontal axis denote time (1.6 s total from top to bottom); and momentum spread (1% full scale) respectively. There are 5 injections-cooling stacking sequences every 300ms 7.8x108 cold ions before bunching ~30% off wrt Nominal value Jocelyn TAN CERN AB / BI

  14. MOMENTUM full span is equivalent to Dp/p = 1% Jocelyn TAN CERN AB / BI

  15. VERTICAL full span is equivalent to Dp/p = 1% Jocelyn TAN CERN AB / BI

  16. Summary • Schottky system in LEIR is fully operational • GUI displaying e.g. tune vs time is expected for the next run • The pick-ups for high momentum have been commissioned, but never used Jocelyn TAN CERN AB / BI

  17. PERFORMANCES :NOMINAL Sigma[mm] 30 H 20 10 0 V Courtesy M. CHANEL, G. TRANQUILLE Jocelyn TAN CERN AB / BI Evolution of beam dimensions during injection and cooling process

  18. Putting numbers : injection • Number of particles 2.25x108 ions • In all formula, replace “e” by “Ze” • Qh / Qv 1.82 / 2.72 • Betatron function bh/bv = 6.5 / 5.5 • Striplines geometry 16cm/13cm • Transfer function Jocelyn TAN CERN AB / BI

  19. Injection: Longitudinal spectrum After e-cooling Injection 6 Jocelyn TAN CERN AB / BI

  20. Injection : Transverse spectra Horizontal e*h= 0.3 p.mm e*h= 1.7 p.mm Vertical e*v= 0.25 p.mm e*v= 1 p.mm Jocelyn TAN CERN AB / BI

  21. Equivalent input noise (1) • Noise Figure of an amplifier : NF [dB] • Passive components • Transistors : Shot noise • FETs : voltage and current noise • Equivalent noise source real G + RinTeq real ideal xG Ieq(f) Rs, T ideal Rs real real world equivalent circuit • Johnson noise of a resistor: R real R, T iR(f) ideal • Equivalent input noise Jocelyn TAN CERN AB / BI

  22. Equivalent input noise (2) G + RinTeq LNA NF1 50 Load Eq. Noise Ieq(f) [pA/Hz1/2] Low Noise Amplifier Zin = 50 NF1 = 1.2 dB NF1 T = Room Temp. 293K 10.3 LNA NF Ieq (f) Teq = 93K 5.8 With active loads the input noise is decreased by ~-6dB LN2 5.3 Teq 10K 1.9 Jocelyn TAN CERN AB / BI

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