Beam Diagnostics Seminar, Nov.05, 2009 Das Tune-Meßverfahren für das neue POSI am SIS-18 U. Rauch GSI - Strahldiagnose

Udo Rauch Beam Diagnostics Seminar, Nov.05, Outline  Brief introduction to SIS-18 accelerator at GSI and motivation  The Libera position data system for tune  System setup  Typical position and tune track  Required beam excitation  Selected results  Space charge effects  Using RF for gating  Tune accuracy  Summary and outlook.

Udo Rauch Beam Diagnostics Seminar, Nov.05, SIS-18 synchrotron at GSI Important parameters of SIS-18: - Circumference 216 m - Inj. typeMultiturn - Energy range 11 MeV → 2 GeV - Acc.RF 0.8 → 5 MHz - Acc. harmonic 4 (no. of bunches) - Bunching factor0.6 → Ramp duration 0.3 → 1.5 s - Typical tune h/v Ion range (Z)1 → 92 (p to U) - Design beams2 x 10¹¹ U x 10¹³ p

Udo Rauch Beam Diagnostics Seminar, Nov.05, SIS-18 synchrotron at GSI Important parameters of SIS-18: - Circumference 216 m - Inj. typeMultiturn - Energy range 11 MeV → 2 GeV - Acc.RF 0.8 → 5 MHz - Acc. harmonic 4 (no. of bunches) - Bunching factor0.6 → Ramp duration 0.3 → 1.5 s - Typical tune h/v Ion range (Z)1 → 92 (p to U) - Design beams2 x 10¹¹ U x 10¹³ p Time span each 2.4 µs 1.6 ms after injection at 0.8 MHz 473 ms after injection at 4.2 MHz

Udo Rauch Beam Diagnostics Seminar, Nov.05, Motivation  Necessity of measurement system arises due to upgrade of existing accelerator SIS-18 for higher beam intensities and/for future accelerator(s) in FAIR project  Target  First of all: Single Bunch Position Measurement with a resolution better than 0.1mm  BaseBand – q measurement with bright signal intensity in order to use minimal or even no beam excitation  Single bunch separation  Future: (PLL) tune tracking  Due to the BPM upgrade process tune can be extracted out of high resolution position data

Udo Rauch Beam Diagnostics Seminar, Nov.05, Outline  Brief introduction to SIS-18 accelerator at GSI and motivation  The Libera position data system for tune  System setup  Typical position and tune track  Required beam excitation  Selected results  Space charge effects  Using RF for gating  Tune accuracy  Summary and outlook.

Udo Rauch Beam Diagnostics Seminar, Nov.05, What is Libera  Instrumentation Technology (I-Tech) – Libera is an integrated setup using a high resolution ADC for onboard data processing on a FPGA  Input actually is one BPM per Libera: 2 channels horizontally and 2 channels vertically  Data will be processed online delivering beam position data in packets to CCCP (presently under hard progress)  Use positions and look at periodicities: Frequency spectrum amplifier ADC and position evaluation Computer in control room amplifier pick up 4 channel ADC 125 MSa / s per channel 14 bit resolution (11 bit effectively) 256 Mb onboard memory

Udo Rauch Beam Diagnostics Seminar, Nov.05, What is tune -Machine intrinsic value: characteristic frequency of the Magnet Lattice (given by the strength of the quadrupole magnets) -Tune should always have a fractional part because of resonances -This fractional part can be measured only! (due to undersampling) -Can be excited directly for measuring purpose

Udo Rauch Beam Diagnostics Seminar, Nov.05, Motivation for digital measuring method  One point per integrated bunch  -> shift of all tune frequencies to baseband due to bunch-wise “sampling rate”  For digital method bunching factor, baseline shift and frequency range is no problem due to digital data treatment  Averaging noise power (thermal noise and digitization noise) by factor of 500 thanks to integration of bunch data (Frequency range 50 MHz -> kHz) (This alone means increase in S/N of position data by 27 dB)  Bunch tracing and Bunch-wise tune separation by software What is needed for position calculation:  Windowing data stream for bunch integration  Baseline restoring (due to AC coupling)  Simple mathematics: K = Sondenkonstante K O = Offset

Udo Rauch Beam Diagnostics Seminar, Nov.05, Position determination: windowing K = Sondenkonstante K O = Offset

Udo Rauch Beam Diagnostics Seminar, Nov.05, Position determination: windowing

Udo Rauch Beam Diagnostics Seminar, Nov.05, Results: Position and Tune Corresponding to 250 ms

Udo Rauch Beam Diagnostics Seminar, Nov.05, Some results: Beam Position and Tune Corresponding to 250 ms

Udo Rauch Beam Diagnostics Seminar, Nov.05, Beam Excitation using Noise Generator Frequency spectrum of noise exciter Matched to RF thus exciting directly on sidebands

Udo Rauch Beam Diagnostics Seminar, Nov.05, Beam excitation w noise Argon18+ beams 11 -> 300 MeV About 1e10 particles

Udo Rauch Beam Diagnostics Seminar, Nov.05, Beam Excitation using Noise Generator  Keeping noise as low as possible: using the IPM (Ionizing Profile Monitor) in order to estimate disturbance of beam profile by noise excitation Defining working Area without Profile broadening

Udo Rauch Beam Diagnostics Seminar, Nov.05, About Signal to noise Signal of baseband tune out of digitized data with noise excitation on lower side of working area is above noise with a level of 34 to 43 dB. This means a power ratio of 50 to 141 in between. As Tune signal amplitude is nearly independent of number of particles due to precise position data, this video is exemplary for tune measurements

Udo Rauch Beam Diagnostics Seminar, Nov.05, How it will be implemented in future

Udo Rauch Beam Diagnostics Seminar, Nov.05, Data acquisition through Libera system pick up amplifier position evaluation Shift to frequency domain tune? K = Sondenkonstante K O = Offset

Udo Rauch Beam Diagnostics Seminar, Nov.05, Outline  Brief introduction to SIS-18 accelerator at GSI and motivation  The Libera position data system for tune  System setup  Typical position and tune track  Required beam excitation  Selected results  Space charge effects  Using RF for gating  Tune accuracy  Summary and outlook.

Udo Rauch Beam Diagnostics Seminar, Nov.05, Space charge effects: coherent motion  Tune frequency is shifted due to self-fields of particles, depending on the amount of particles. Space charge introduces an additional acceleration force to the individual particle motion  The collective betatron motion is influenced by space charge, as it acts on the beam with well determined phase. This leads to frequency shift  Coherent motion changes absolute value of tune  Incoherent motion changes width of observed frequency

Udo Rauch Beam Diagnostics Seminar, Nov.05, Space charge effects: coherent motion Space charge coherent tune shift on vertical tune: Tune is shifted by up to 12 mq to lower frequency No observable effect on horizontal tune (maybe due to less sensitivity of pickup in horizontal plane and no possibility to excite beam)

Udo Rauch Beam Diagnostics Seminar, Nov.05, Position determination: windowing  Why not taking the RF? It is bunch- synchronuos, free-to-use and matched to the width of every bunch. Or not?

Udo Rauch Beam Diagnostics Seminar, Nov.05, Position determination: windowing Thus RF cannot be used, presumably due to cable mismatching; The gating of data has to be done on data itself

Udo Rauch Beam Diagnostics Seminar, Nov.05, Conclusions  It has been shown, that position and tune is measured stable for all types of ions and different number of particles with a resolution better than 0.1mm and at least 1mq for position and tune respectively  Data is ready to run online  Physical observations are possible thanks to a high resolution measurement (e.g. space charge, quadrupol oscillations, influence of chromaticity))  Next step is to implement this to an automatic correction system based on obtained position and tune data (Rahul) Thank you for Your attention!

Udo Rauch Beam Diagnostics Seminar, Nov.05,

Udo Rauch Beam Diagnostics Seminar, Nov.05,

Udo Rauch Beam Diagnostics Seminar, Nov.05, Data acquisition through Libera system pick up amplifier position evaluation Shift to frequency domain tune? K = Sondenkonstante K O = Offset

Udo Rauch Beam Diagnostics Seminar, Nov.05, Some Inputs for the tune calculation

Udo Rauch Beam Diagnostics Seminar, Nov.05, Outline  Brief introduction to accelerators at GSI and motivation  The Libera position data system for tune  Some results  Typical position and tune track  Required excitation level and influence on beam  Tune accuracy  Summary and outlook.