Impedances of Laminated Vacuum Chambers

Burov, A.; Lebedev, Valeri

doi:10.2172/1021483

Cited by 5 publications

(10 citation statements)

References 6 publications

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“…While this approximation works for metallic pipes, it produces wakes which are too large for laminated chambers. In parallel with our work, an independent derivation of the impedance in laminated structures was done by Burov and Lebedev in [11]. Their results, albeit derived in a different way, are in agreement with ours.…”

Section: Introductionsupporting

confidence: 87%

Coupling impedance and wake functions for laminated structures with an application to the Fermilab Booster

Macridin

Spentzouris

Amundson

et al. 2011

Phys. Rev. ST Accel. Beams

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We calculate the impedance and wake functions for laminated structures with parallel-plane and circular geometries in the ultrarelativistic limit. We critically examine the approximations used in the literature for the coupling impedance in laminated chambers and find that most of them are not justified because the wall surface impedance is large. A comparison between flat and circular geometry impedances is presented. We apply our calculation in a state-of-the-art beam dynamics simulation of the Fermilab Booster which includes nonlinear optics, laminated wakefields, and space charge impedance. The latter can have a significant effect away from the ultrarelativistic limit. Even though the simulations and the comparison with the experiment are done at the Booster injection energy, where the relativistic factor ¼ 1:42, we find good agreement between our calculation of the coherent tune shift and recent experimental measurements.

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Section: Introductionsupporting

confidence: 87%

Coupling impedance and wake functions for laminated structures with an application to the Fermilab Booster

Macridin

Spentzouris

Amundson

et al. 2011

Phys. Rev. ST Accel. Beams

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“…In the context of the rigid beam model, for a coasting beam with Gaussian distributions (both longitudinally and transversely) and assuming that the main reason for the frequency spread (for the resonant particles) is the chromaticity, the stability threshold follows [4] (2) with λ as the linear density, C the orbit circumference and r p the proton classical radius, ε T nrms is the rms normalized transverse emittance and ∆ν c is the wake-driven coherent tune shift, see e. g. [7]: Y F = ) It should be noted that, the model presented here [4] uses a more realistic beam particle distribution for space-charge tune shift calculations than a similar model from Ref. [3] and gives ≈ 40% higher instability threshold.…”

Section: Phase Density Instability Thresholdmentioning

confidence: 99%

“…Therefore, in theory, since the Landau damping rate is proportional to the beam distribution function integrated over its transverse actions, it is necessary to know the details of the distribution f to determine if the beam will go unstable or not. For instance, calculations of D th,95 for a Gaussian and a step-like distribution find that it is ~2 times higher for the Gaussian distribution than for the step-like distribution [4]. Unfortunately, in operation, there is no measurement that can resolve quantitatively the amount of tail particles so that we could exactly predict (thus avoid) the instability to occur.…”

Section: Importance Of the Beam Distribution In The Determination Of mentioning

confidence: 99%

“…In the effort to provide higher integrated luminosity for the experiments, the number of antiprotons stored in the Recycler continually increased and reached up to 500×10 10 particles. At this level (~400×10 10 and higher), the antiproton beam is subject to a transverse instability [2,3,4] during the RF manipulation [5] necessary for extraction to the Tevatron, while cooling is also the strongest. In other words, the transverse instability sets the maximum brightness of the antiproton beam that can be delivered to the downstream machines and in turn the overall efficiency for the number of antiprotons available for collision.…”

Section: Introductionmentioning

confidence: 99%

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Transverse Instabilities in the Fermilab Recycler

Prost¹,

Burov²,

Shemyakin³

et al. 2011

Self Cite

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Transverse instabilities of the antiproton beam have been observed in the Recycler ring soon after its commissioning. After installation of transverse dampers, the threshold for the instability limit increased significantly but the instability is still found to limit the brightness of the antiprotons extracted from the Recycler for Tevatron shots.In this paper, we describe observations of the instabilities during the extraction process as well as during dedicated studies. The measured instability threshold phase density agrees with the prediction of the rigid beam model within a factor of 2. Also, we conclude that the instability threshold can be significantly lowered for a bunch contained in a narrow and shallow potential well due to effective exclusion of the longitudinal tails from Landau damping.

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“…The results for a circular beam pipe are reported in Ref. [5] and the interested reader can find the closed analytical formulae in Ref. [6].…”

Section: Circular Steel Tubementioning

confidence: 99%

Bench measurements of low frequency transverse impedance

Mostacci¹,

Caspers

Iriso

Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440)

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For frequencies below 10 MHz the classical two wire transmission line method is subject to difficulties in sensitivity and measurement uncertainties. Thus for evaluation of the low frequency transverse impedance properties of the LHC dump kicker a modified version of the two wire transmission line has been used. It consists, in the present case, of a 10 turn loop of approximately 1 meter length and 2 cm width. The change of input impedance of the loop is measured as a function of the surroundings and by using a proper reference (metallic beampipe) these changes are converted into a meaningful transverse beam coupling impedance. Measurements of several calibration objects have shown close agreement with theoretical results. For frequencies below 10 MHz the classical two wire transmission line method is subject to difficulties in sensitivity and measurement uncertainties. Thus for evaluation of the low frequency transverse impedance properties of the LHC dump kicker a modified version of the two wire transmission line has been used. It consists, in the present case, of a 10 turn loop of approximately 1 meter length and 2 cm width. The change of input impedance of the loop is measured as a function of the surroundings and by using a proper reference (metallic beam pipe) these changes are converted into a meaningful transverse beam coupling impedance. Measurements of several calibration objects have shown close agreement with theoretical results. EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH CERN -AB Division

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Impedances of Laminated Vacuum Chambers

Abstract: Longitudinal and transverse impedances are derived for round and flat laminated vacuum chambers.

Cited by 5 publications

References 6 publications

Coupling impedance and wake functions for laminated structures with an application to the Fermilab Booster

Coupling impedance and wake functions for laminated structures with an application to the Fermilab Booster

Transverse Instabilities in the Fermilab Recycler

Bench measurements of low frequency transverse impedance

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