Filters

Results

**1**-**10**of**164** Results

**1**-**10**of**164**. Search took:**0.018**secondsSort by: date | relevance |

Chao, A.W.

Stanford Linear Accelerator Center, CA (USA)

Stanford Linear Accelerator Center, CA (USA)

AbstractAbstract

[en] A matrix formalism for polarization calculation, as well as its comparison with other methods, is briefly discussed. The prediction for SPEAR is compared with experimental measurements. An estimate is offered for the transverse polarization for PEP. Various schemes for obtaining the longitudinal polarization in PEP are studied

Primary Subject

Source

Sep 1980; 11 p; International symposium on H.E. physics with polarized beams and polarized targets; Lausanne, Switzerland; 25 Sep - 1 Oct 1980; CONF-800994--8; Available from NTIS., PC A02/MF A01

Record Type

Report

Literature Type

Conference

Report Number

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

Chao, A.W.

Stanford Linear Accelerator Center, Menlo Park, CA (USA)

Stanford Linear Accelerator Center, Menlo Park, CA (USA)

AbstractAbstract

[en] The particle distribution in an ideal electron storage ring is well known to be gaussian with infinitely long beam lifetime. It is also clear that in reality an aperture long beam lifetime. It is also clear that in reality an aperture limit due to finite vacuum chamber size will truncate the gaussian distribution in the tail and introduce a finite lifetime. This disturbed distribution and the associated quantum lifetime have been obtained for a one-dimensional case in a previous note. One has to perform a more complicated two-dimensional calculation with both the betatron and synchrotron motions taken into consideration. In this note we shall attempt to find an approximate expression of the beam lifetime for this two-dimensional problem. 3 refs

Primary Subject

Secondary Subject

Source

May 1976; 10 p; Available from NTIS, PC A02/MF A01 - OSTI; 1 as DE89004596; Portions of this document are illegible in microfiche products.

Record Type

Report

Report Number

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

Chao, A.W.

Stanford Linear Accelerator Center, Menlo Park, CA (USA)

Stanford Linear Accelerator Center, Menlo Park, CA (USA)

AbstractAbstract

[en] One possible feedback system, designed mainly for damping the longitudinal dipole oscillations, utilizes a beam position monitor and an rf cavity. The horizontal displacement of the beam is measured at the monitor and the measurement is sent to the rf cavity. The phase of the cavity voltage is then adjusted so that an electron changes its energy by the additional amount of Δ/var epsilon/ = /zeta/E/sub o/x/sub monitor/. This FB system introduces damping or anti-damping to the horizontal betatron oscillation and the longitudinal synchrotron oscillation. Although approximate expressions for the associated damping constants α/sub x,s/ can be obtained by elementary considerations, it is perhaps constructive to have an exact calculation available as well. In the following, we will describe the exact calculation; obtain approximate expressions of α/sub x,s/ from the exact calculation; obtain approximate expressions of Δν/sub x,s/, the coherent tune shifts caused by the FB systems; and numerically compare the exact and approximate results under various conditions. We assume that there is only one active rf cavity in the storage ring and that the monitor signal reaches the rf cavity before the beam completes one turn. 5 refs., 6 figs

Primary Subject

Source

Jun 1978; 13 p; Available from NTIS, PC A03/MF A01 - OSTI; 1 as DE89006225; Portions of this document are illegible in microfiche products.

Record Type

Report

Report Number

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

Chao, A.W.

Stanford Linear Accelerator Center, Menlo Park, CA (USA)

Stanford Linear Accelerator Center, Menlo Park, CA (USA)

AbstractAbstract

[en] The stationary distribution function for an ensemble of one-dimensional simple harmonic oscillators in the presence of damping and random excitation has been shown to be gaussian in its oscillation amplitude. Aside from the fact that no nonlinearities are included, this result has the limitation that it is true only when the oscillation amplitude is unlimited. In an electron storage ring, for example, the amplitude will have to be bounded by the vacuum chamber walls. It is clear that the gaussian distribution,having an infinitely long tail, will have to be modified. Furthermore, since electrons will be lost once they hit the vacuum chamber wall, a stationary distribution with infinite lifetime will no longer exist. The electron bunch will then have a finite lifetime. It is the purpose of this note to find this distribution function and lifetime in the presence of vacuum chamber walls. Only a one-dimensional case will be considered. In this paper, we will set up the partial differential Fokker-Plack equation for the distribution function. An outline of the procedure to solve this equation is then given in the third section. In general, the solution involves an infinite power series and a numerical calculation will have to be used. If, however, the vacuum chamber limit is much larger (valid for electrons) or much smaller (valid for protons) than the ''natural'' beam size, the problem can be greatly simplified. These simplified cases will be treated in the last two sections. 2 refs., 2 figs

Primary Subject

Source

Dec 1975; 10 p; Available from NTIS, PC A02/MF A01; 1 as DE88014828; Portions of this document are illegible in microfiche products.

Record Type

Report

Report Number

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

Chao, A.W.

Lawrence Berkeley Lab., CA (USA). SSC Central Design Group

Lawrence Berkeley Lab., CA (USA). SSC Central Design Group

AbstractAbstract

[en] This paper discusses the following concepts related to nonlinear dynamics in storage rings: canonical perturbation theory; resonances; Hamilton-jacobi equations; tracking simulations; explicit canonical integration; taylor and lie maps; and differential algebra

Primary Subject

Source

Sep 1988; 5 p; Applied superconductivity conference; San Francisco, CA (USA); 21-26 Sep 1988; CONF-8809486--4; CONTRACT AC02-89ER40486; NTIS, PC A02/MF A01 as DE90013041; OSTI; INIS

Record Type

Report

Literature Type

Conference

Report Number

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

Chao, A.W.

Stanford Linear Accelerator Center, CA (USA)

Stanford Linear Accelerator Center, CA (USA)

AbstractAbstract

[en] The field of beam polarization in electron storage rings is making rapid progress in recent several years. This report is an attempt to summarize some of these developments concerning how to produce and maintain a high level of beam polarization. Emphasized will be the ideas and current thoughts people have on what should and could be done on electron rings being designed at present such as HERA, LEP and TRISTAN. 23 references

Primary Subject

Source

1983; 7 p; Particle accelerator conference; Santa Fe, NM (USA); 21-23 Mar 1983; CONF-830311--152; Available from NTIS, PC A02/MF A01 as DE83012764

Record Type

Report

Literature Type

Conference

Report Number

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

Chao, A.W.

Lawrence Berkeley Lab., CA (USA). SSC Central Design Group

Lawrence Berkeley Lab., CA (USA). SSC Central Design Group

AbstractAbstract

[en] The description of the motion of charged-particle beams in an accelerator proceeds in steps of increasing complexity. The first step is to consider a single-particle picture in which the beam is represented as a collection on non-interacting test particles moving in a prescribed external electromagnetic field. Knowing the external field, it is then possible to calculate the beam motion to a high accuracy. The real beam consists of a large number of particles, typically 10

^{11}per beam bunch. It is sometimes inconvenient, or even impossible, to treat the real beam behavior using the single particle approach. One way to approach this problem is to supplement the single particle by another qualitatively different picture. The commonly used tools in accelerator physics for this purpose are the Vlasov and the Fokker-Planck equations. These equations assume smooth beam distributions and are therefore strictly valid in the limit of infinite number of micro-particles, each carrying an infinitesimal charge. The hope is that by studying the two extremes -- the single particle picture and the picture of smooth beam distributions -- we will be able to describe the behavior of our 10^{11}-particle system. As mentioned, the most notable use of the smooth distribution picture is the study of collective beam instabilities. However, the purpose of this lecture is not to address this more advanced subject. Rather, it has the limited goal to familiarize the reader with the analytical tools, namely the Vlasov and the Fokker-Planck equations, as a preparation for dealing with the more advanced problems at later times. We will first derive these equations and then illustrate their applications by several examples which allow exact solutionsPrimary Subject

Source

Jan 1987; 48 p; 2. joint US/CERN school on particle accelerators: frontiers of particle beams; South Padre Island, TX (USA); 23-29 Oct 1986; CONF-8610108--9; CONTRACT AC02-89ER40486; NTIS, PC A03/MF A01 as DE90014551; OSTI; INIS; US Govt. Printing Office Dep

Record Type

Report

Literature Type

Conference

Report Number

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

Chao, A.W.

Stanford Linear Accelerator Center, Menlo Park, CA (USA)

Stanford Linear Accelerator Center, Menlo Park, CA (USA)

AbstractAbstract

[en] In the study of beam-cavity coupling effects, one must solve Maxwell's equations for the fields produced by a given beam shape and given cavity geometry. A recent paper that treats the effect on the bunch shape has considered the longitudinal electric field in a pill box cavity produced by a step function charge pulse traveling at the speed of light. In order to obtain a clear physical picture of how the fields are produced in the cavity, we treat the problem of a point charge traveling at the speed of light, c, between two infinite plates. This must, of course give the same result as the closed pill box cavity for values of time t such that ct is less than the cavity radius. In this paper, the longitudinal and radial electric field components and the azimuthal magnetic field component are derived from Maxwell's equation for this idealized case. We use the eigenmode expansion method and include some details of the tricks used in the computation of the sums. We also discuss the physical picture of the electromagnetic fields that were derived. 5 refs., 3 figs

Primary Subject

Source

10 Feb 1975; 11 p; Available from NTIS, PC A03/MF A01; 1 as DE88013655; Portions of this document are illegible in microfiche products.

Record Type

Report

Report Number

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

Chao, A.W.

Lawrence Berkeley Lab., CA (USA). SSC Central Design Group

Lawrence Berkeley Lab., CA (USA). SSC Central Design Group

AbstractAbstract

[en] In the spring of 1984, a reference designs study (RDS) was carried out to identify the issues and to provide a crude cost estimate of the SSC. Following the RDS, a Central Design Group was formed in October to perform the detailed design R ampersand D for construction of the SSC. This paper is a brief review of progress made on the accelerator physics studies since October 1984. For major issues not discussed here, many of them of great importance, the RDS report is still the valid source of information. 29 refs., 6 figs

Primary Subject

Secondary Subject

Source

1985; 6 p; CONTRACT AC02-89ER40486; NTIS, PC A02/MF A01 as DE90014088; OSTI; INIS; US Govt. Printing Office Dep

Record Type

Report

Report Number

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

Chao, A.W.

Lawrence Berkeley Lab., CA (USA). SSC Central Design Group

Lawrence Berkeley Lab., CA (USA). SSC Central Design Group

AbstractAbstract

[en] An elementary description of the accelerator physics considerations encountered in the design of the Superconducting Super Collider is presented. An attempt has been made to introduce the terminology and the basic physics issues from a user's point of view. 15 refs., 12 figs., 1 tab

Primary Subject

Secondary Subject

Source

1985; 17 p; 1985 annual DPF conference; Eugene, OR (USA); 13-16 May 1985; CONF-8505405--1; CONTRACT AC02-89ER40486; NTIS, PC A03/MF A01 as DE90014010; OSTI; INIS; US Govt. Printing Office Dep

Record Type

Report

Literature Type

Conference

Report Number

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

1 | 2 | 3 | Next |