Chromaticity tracking with a phase modulation/demodulation technique in the Tevatron

Tan, Cheng‐Yang

doi:10.1016/j.nima.2009.01.132

Cited by 2 publications

(3 citation statements)

References 6 publications

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“…The BTF for the two rf frequency changes AE40 Hz and the nominal rf frequency at zero frequency change are measured for both uncoalesced and coalesced beam. The phase of the BTF is recorded and used for the analysis because of the way linear chromaticity is measured with a phase locked loop (PLL) based chromaticity tracking system where only the ''zero'' crossings of the phase response matter [9]. Figures 6 and 7 show the typical phase of the BTF measurements for three different 0 changes.…”

Section: A Btf Experimentsmentioning

confidence: 99%

Effect of impedance and higher order chromaticity on the measurement of linear chromaticity

Ranjbar

Tan

2011

Phys. Rev. ST Accel. Beams

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The combined effect of impedance and higher order chromaticity can act on the beam in a nontrivial manner which can cause a tune shift which depends on the relative momenta with respect to the ''on momentum'' particle (Áp=p). Experimentally, this tune shift affects the measurement of the linear chromaticity which is traditionally measured with a change of Áp=p. The theory behind this effect will be derived in this paper. Computer simulations and experimental data from the Tevatron will be used to support the theory.

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Section: A Btf Experimentsmentioning

confidence: 99%

Effect of impedance and higher order chromaticity on the measurement of linear chromaticity

Ranjbar

Tan

2011

Phys. Rev. ST Accel. Beams

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“…Another fast technique allowing continuous measurement is based upon RF phase modulation/demodulation using dedicated Chromaticity Tracker (CT) hardware. When modulating the RF phase at a set amplitude and frequency, the chromaticity can be extracted from the relation Q' = η[(k+q 0 ) -hZ / Δ φ mod )], where Δφ mod is the amplitude of the phase modulation, Z is the measured amplitude of the demodulated phase signal, q 0 is the measured fractional tune from the Tune Tracker, η = 0.0029 is the momentum compaction factor, k = 448 is the mode number, and h = 1113 is the RF harmonic number [32]. 4ns) of a high intensity proton bunch in the Tevatron at 150 GeV vs turn number after a 1 mm vertical kick.…”

Section: Chromaticity Diagnosticsmentioning

confidence: 99%

“…b) (bottom) Horizontal and vertical chromaticity drifts in the Tevatron at 150 GeV (with imperfect compensation) as measured continuously by the Chromaticity Tracker. In the gray region, beam was injected and chromaticity set to 4 units in both planes [32].…”

Section: Chromaticity Diagnosticsmentioning

confidence: 99%

Beam instrumentation for the Tevatron collider

2009

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The Tevatron in Collider Run II (2001-present) is operating with six times more bunches and many times higher beam intensities and luminosities than in Run I (1992)(1993)(1994)(1995). Beam diagnostics were crucial for the machine start-up and the never-ending luminosity upgrade campaign. We present the overall picture of the Tevatron diagnostics development for Run II, outline machine needs for new instrumentation, present several notable examples that led to Tevatron performance improvements, and discuss the lessons for future colliders. FIGURE 2. a) (top) Evolution of beam losses (left axis) in 2002-2009.Red shows fractional loss of antiprotons between injection into the Tevatron and start of collisions, next (blue) one is for loss of protons, greenfractional reduction of the luminosity integral caused by beam-beam effects in collisions. b) (bottom) Injection process and beginning of the luminosity run in store #7040 (May 11, 2009). The square dots are the total proton and antiproton bunch intensities, respectively, as measured by the Fast Bunch Integrator (FBI) system. The line on the right represents the start of the HEP store with an initial peak luminosity of 321×10 30 cm -2 s -1 . The spikes in the beam intensities are instrumentation artifacts that occur when antiproton bunches pass through proton bunch integration gates during longitudinal cogging [1]. 4 BEAM DIAGNOSTICS DEVELOPMENTSOperation of a superconducting magnet hadron collider, like Fermilab's Tevatron, requires a great deal of care, understanding of beam conditions, and trust in the beam diagnostics, because comparatively innocent little imperfections can lead to either beam blow-up and luminosity loss or to beam loss and quench of SC magnets. In the Tevatron such a quench results in 2-4 hours of magnet recovery time and up to 8-16 hours of no-luminosity time needed to produce the antiprotons needed for the next High Energy Physics (HEP) store. Over 8 years of operations we witnessed machine downtimes due to 0.5-1% of beam intensity loss, poor beam lifetime, 0.5-1 mm orbit error, collimator malfunctioning, sequencer error, excursions of tunes or coupling of the order of few 0.001 or several units of chromaticity, instability occurrences, or malfunctioning of kickers, high voltage electrostatic separators, or one of hundreds of power supplies, etc. Naturally, these peculiarities were reflected in the kinds of beam diagnostics we developed (e.g. minimization of their invasiveness) and the way they were exploited (fast data-logging, convenience for post-mortem analysis, etc.).In the Tevatron, the protons and antiprotons circulate within a single beam pipe, so electrostatic separators are used to kick the beams onto distinct helical orbits to allow head-on collisions only at the desired interaction points. (See Fig. 3.) At 150 GeV, separation is limited to ~(10-22) mm by physical aperture, while the separation above 600 GeV, ~(3-6 mm), is limited by the breakdown (spark) rate of the separators at high voltage. Long-range beam effects degrade beam...

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Chromaticity tracking with a phase modulation/demodulation technique in the Tevatron

Cited by 2 publications

References 6 publications

Effect of impedance and higher order chromaticity on the measurement of linear chromaticity

Effect of impedance and higher order chromaticity on the measurement of linear chromaticity

Beam instrumentation for the Tevatron collider

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