|
|
NUMBER
|
DATE
|
TITLE
|
AUTHOR
|
ABSTRACT
|
60
|
08/08/2001 |
Considerations
about Pb ions at injection plateau of the SPS |
L.Vos |
I
compute the space charge tune shift and give estimations of intra beam
scattering behaviour of lead ion bunches intended for collisions in the
LHC at the injection plateau of the SPS for several scenarios. |
|
59
|
28/06/2001 |
Symplectic matrix
Algebra |
J. M. Jowett |
This note documents
a Mathematica package for working with symplectic matrices. The illustrative
examples include the use of the symplectic unit matrices, the symplectic
conjugate and the manipulation of exact and approximate matrices including
the symbolic representation of a combined-function bending magnet. A function
to symplectify matrices is provided. Like the other functions in the packages
it works on matrices of any even dimension to arbitrary precision (examples
are given for 16 digits, 99 digits and infinite precision). |
|
58
|
.06/07/2001 |
Tracking to verify the IR3
design for Version 6.2 |
D. Kaltchev |
This report outlines
a simple procedure, based on off-momentum tracking of ~10^3 halo particle
per dp/p value, sufficiently accurate to verify the IR3 ideal design
parameters (also enumerated here). The lattice section used begins at the
primary collimator in IR3 and extends for one turn around the ring. We
use the error-free thick element optics for Beam 1, Version 6.2. The procedure
will be further extended to study halo propagation with collimator misalignment
and optical errors. |
|
57
|
23/05/2001 |
Self-Consistent
LHC bunch orbits for asymmetric injection schemes |
H. Grote |
The nominal LHC injection
scheme assumes symmetry in the bunch population of ring-1 and ring-2 with
respect to IP1 and IP5, where the first bunch of ring-1 collides with the
first bunch of ring-2, and so on. Here we study the effect on the self-consistent
closed orbits when this symmetry point is moved either to IP2 (and IP6),
or to the centre of an arc. |
|
56
|
03/04/2001 |
SODD: A Physics Guide |
F. Schmidt |
The Program SODD (Second
Order Detuning and Distortion function) calculates
the detuning distortion and Hamiltonian terms for arbitrary complex accelerators
structures up to second order in the four-dimentional phase space. Starting
from the linear lattice functions and the strength of the multipoles these
terms are determined in first order of the multipole strength and in second
order of all possible pairs of multipoles. This report documents the formulae
of the various terms as coded in the program. |
|
55
|
06/03/2001 |
Focusing at low energy |
A. Verdier |
The merits of FODO and FO cells
are compared. It appears that cylindrical magnetics lenses could be attractive
for the first circulator of the neutrino factory thanks to their better
optics performance, simpler design.and possible integration in the RF cavities.
Some more studies are needed to assess the actual potentialities of cylindrical
lenses and to launch a possible optimisation. |
|
54
|
09/02/2001 |
What is the operational
scenario required for the spectrometer magnets in IP2 and IP8 |
W. Herr |
Following a discussion with
P. Proudlock and a request in a recent meeting of the Performance and Layout
Committee (31.01.01) I should like to present the constraints for the operation
of spectrometers in IP2 and IP8 during the injection process. |
|
53
|
18 Jan 01 |
Run Environment for SixTrack |
F. Schmidt |
This note will describe how
massive tracking campaigns can be performed with SixTrack starting from
a MAD input file of the LHC lattice. The idea is to launch these runs as
automatic as possible with minimal knowledge of either UNIX scripts or
SixTrack input. |
|
52
|
18 Dec 00 |
The Syndrome of the Closed
Orbit Correction in the LHC Arcs |
S. Fartoukh |
This paper presents analytical
results concerning the closed orbit corrector system of the LHC arcs. |
|
51
|
18 Dec 00 |
Damping Wiggler Section
for CLIC |
F. Zimmermann |
Considering a damping ring
where radiation damping, quantum excitation and intrabeam scattering only
occur in a few long wiggler sections - the rest of the ring being transparent
-, I show that by a proper choice of wiggler strength, wiggler period,
beta function, and beam energy, the CLIC design emittances and damping
rates may be attained. |
|
50
|
24 Nov 00 |
Considerations about the Impedance of the Y-Chamber
|
L. Vos |
Two particular aspects of the
impedance of the Y-chamber designed by LBL are studied. The first aspect
is the low frequency (inductive) impedance. The second aspect is the possible
existence of a resonant mode which has the appearance of a trapped mode.
The basic geometry of the Y-chamber is circular but for computational ease
a rectangular geometry has been simulated with MAFIA by B. Spataro [1].
The results obtained by the simulation are very interesting and merit further
thought and reflection. I will consider the rectangular geometry and try
to estimate analytically the low frequency impedance. I then consider the
possibility of a trapped mode in the same geometry. I conclude by making
impedance predictions about the (real) circular chamber which cannot be
carried out with simulation programs according to our present understanding. |
|
49
|
8 Nov 00 |
BPM resolution and beam threading in the LHC
|
L. Vos |
The threader in MAD-8 has been
used to study first turn conditions for different values of the BPM resolution,
the quadrupole alignment error, with and without correction of the magnetic
field errors. |
|
48
|
7 Nov 00 |
Effect of b3 Error on Nominal and Resonance-free
Lattices with Gradient Errors
|
D. Kaltchev |
We compare de Nominal and Resonance-free
LHC lattices with imposed field errors from table Einj.9901, gradient errors
included, on the basis of their dynamic aperture (MAD8) and driving terms
(code SODD). The beta-mistmatch and ring tune shift are corrected via the
insertion quads. The goal is to test the potency of the resonance-free
scheme to cancel alone the effect of the b3 error and to confirm its resistance
against the b2 error. Without the 3-order spool correction, due to the
systematic b2 changing its sign from inner to outer octant, the optic quality
for Beam 1 and Beam 2 is different. |
|
47
|
27 Oct 00 |
Threader and BPM's accuracy
|
A. Verdier |
The BPM's accuracy for a first
turn is evaluated as a funciton of the threader performance. It appears
that it is useless to request an r.m.s. accuracy better than 1.5.mm. |
|
46
|
17 Oct 00 |
Do we need to be afraid
of the trapped modes in the liner? |
L. Vos |
Special topic presented at
the SL-AP Thursday Meeting held on October 12th. |
|
45
|
26 Sept 00 |
Effect of a static misalignment
of the CLIC BDS |
A. Verdier |
The tolerances on the transverse
stability of the focusing magnets of the Beam Delivery System of CLIC are
in the nm range. The question addressed here concerns a different
aspect of the problem, i.e. the absolute alignment and its compensation.
The effect of static misalignments have been compensated by means of steering
dipoles which act both on trajectory and dispersion correction. Thanks
to the correction, the toleance on this misalignment is less tight than
the tolerance on stability. However, because of the emittance buildup
associated with synchrotron emission, the tolerance on static misalignment
is found to be in the sub-micron range. |
|
44
|
24 July 00 |
A study of the dynamic aperture
of the LHC at injection with shifts in central beam momentum |
R. Burgess |
We present a short study of
the dynamic aperture and some discussion of the chromatic properties of
LHC optics V6.0 with shifts in the central beam momentum. Within the momentum
window defined for the LHC of Delta-p= + 2 x 10^3 the 1000 turn dynamic
aperture shows an average reduction of approximately 71.4% compared to
the on-momentum dynamic aperture. |
|
43
|
3 May 00 |
Geometric Aspects of the Modeling of the Main
Dipole of the LHC.
|
E. Wildner |
The input for the optics program
MAD is generated from a database that contains information for all elements
in the machine, including geometric positioning of the elements. For optics
calculations we need for each element its position along a coordinate axis
(the "s-coordinate") which means something only if it is coupled to the
model of the bending magnets chosen in the program. This note evaluates
the geometric consequences of changing the model of the main bending magnets,
while keeping the same s-value position for all elements in the machine.
Some indications of how to get around the problem are given. |
|
42
|
12 May 00 |
Geometrical errors for MQ, MB and BPM for C.O.
studies
|
J.B. Jeanneret |
As intermediate short review
of the geometrical errors for MQ, MB and BPM is made to allow for closed
orbit correction evaluation. |
|
41
|
12 May 00 |
Electron capture in Pb-Pb collisions and quench
limit
|
J.B. Jeanneret |
In heavy ion collisions, slightly
inelastic electromagnetic processes have cross-sections much larger than
hadronic processes. Among these processes at least one, the e+e- pair production
followed by the capture of the e-on an atomic shell of one of the ions
can induce distant losses of the ions. In the case of Pb-Pb collisions,
we show that with nominal luminosities, the quench limit is nearly met
in the dispersion suppressor. |
|
40
|
22 Mar 00 |
Tool for calculating the width of resonance islands
from maps
|
L.H.A. Leunissen |
A semi analytical tool is available
to calculate the strength of resonance islands from maps. It is an extension
of an existing tool run_tunrescor as reported in [1], [2]. In contrast
to pure analytical methods [3], this is unlimited by approximations. Also,
islands widths can be calculated for 4D coupling resonance with run_tunrescor_island.
The location of the file is: $AP_GROUP_DIR/share/grr/. |
|
39
|
7 Feb 00 |
Selft consistent beam-beam for round beams
|
A. Verdier |
The linear part of the beam-beam
interaction can be computed in a self consistent way for round beams. It
is shown that this interaction does not induce any linear instability,
in opposite to old naive calculations. The change of both beam size at
the crossing and xi_bb are negligible for LHC. |
|
38
|
13 Dec 99 |
Software Activity in 1999
|
F. Schmidt et al |
The software development on
the various FORTRAN software tools are summarized. Possible implications
for MAD are stated where applicable. |
|
37
|
2 Dec 99 |
Tool for calculating the strength of resonance
from 5D maps
|
P.L.H. Leunissen et al |
A tool to calculate the strength
of resonances from maps. The location of the files is: $AP_GROUP_DIR/share/grr/. |
|
36
|
2 Nov 99 |
Possible Phase-advance per cell for Resonance-freeLattices
|
D. Galletly, A.Verdier |
Most of the systematic non-linear
resonancesassociated with a part of an alternating gradient machine composed
of Nc identical cells can be avoided by a correct choice of the two phase
advancesper cell. A description of how to calculate these values, and various
interesting values of phase advance are given here. A short tracking test
shows the interest of lattices obtained by this procedure. |
|
35
|
22 Oct 99 |
Test of Geometry Calculations in MAD Version 9
|
J.M. Jowett |
The new MAD Version 9 includes
calculations of the machine geometry built up from the description of the
sequence of elements. These are tested by comparison with MAD Version 8
using the example of the LHC. |
|
34
|
3 Aug 99 |
Statistical significance of dynamic aperture calculations
|
H. Grote |
The confidence limits for the
dynamic aperture calculations are derived independent of the underlying
distribution of the values calculated with Monte-Carlo simulations. To
have a 95% confidence that only 5% of the total number of all possible
LHC realisations have a dynamic aperture value lower than the lowest one
found by particle tracking one needs an unbiassed sample of 59 realisations
of the LHC with magnetic field errors. |
|
33
|
16 JULY 99 |
Physical Constants, Notations and Units for Accelerators
Physics
|
R.T. Burgess, J.M. Jowett, |
This note is the documentation
for a Mathematica [1,2] package designed to provide symbols for physical
constants commonly occurring in accelerator physics. The properties of
these symbols include their values and units in a very natural way. In
addition the package provides capabilities for painless conversions between
many systems of units and for checking that the dimensions of expressions
are consistent. Basic use of the package is via a palette of buttons that
will appear on your screen when you load it. |
|
32
|
22 June 99 |
From Loss-less Oscillator to Landau Damping
|
L. Vos |
Copies of transparencies presented
in a one day Thinkshop concerning possible detection of Gravitational Waves
with the LHC. |
|
31Rev
|
5 Nov 99 |
More about a3 syndrome
|
A. Verdier |
This note is a compilation
of what was published in the beam-physics note 31 (providing missing informations
concerning the chromatic coupling on resonance-free lattices), corrections
of this note by S. fartoukh and further computations resulting from discussions
with J.P.Koutchouk and S. fartoukh. It is intended to provide a basis for
further discussion on the usefulness of the a3 correction system. |
|
31C
|
11 June 99 |
Correction to the beam-physics note 31: More about
a3 syndrome
|
A. Verdier |
This note is intended to correct
both wrong and missing information in the beam-physics note 31. The latter
must not be quoted without a careful check of the correction below. |
|
31
|
11 June 99 |
More about a3 syndrome. See also 31C and 31 Rev
|
A. Verdier |
In the presentation of the
effect of the a3 uncertainty to the LHC MAC to justify the a3 compensation
system, two points were missing: the probability of the "worst case" and
the solution to the problem with resonance-free lattices. The aim of this
note is to make this information available. |
|
30
|
2 June 99 |
About the "ATL"
|
A. Verdier |
The "ATL" predicts that "ground
points perform Brownian motion characterised by the variance of the relative
displacement which scales as a product of temporal and spatial intervals"
This law was mentioned at the beam-beam workshop as a reference to describe
the relative motion of magnets. This is critically examined here. |
|
29
|
23 May 99 |
Not published yet
|
J-B. Jeanneret |
. |
|
28
|
23 April 99 |
Beam-Beam effect in LEP, an alternative point
of view..
|
A. Verdier |
The luminosity data provided
by Helmut Burkhardt have been interpreted in term of self-consistent beam-beam
element. Single particle parameters have been calculated with MAD including
this element. It appears that the actual vertical emittance tune shifts
shows that a possible origin of the beam-beam limit could come from Q_x
being close to an half integer. A maximum xi_y of 0.111 is predicted for
operation at 96GeV according to this consideration. |
|
27
|
8 April 99 |
Ripple data
|
A. Verdier |
The effects of power converter
supplies ripples measured in the ISR, Spp-S and HERA have been compiled.
They can be used to produce tolerances for LHC. |
|
26
|
17 Mar 99 |
Equivalence classes of beam-beam encounters in
the LHC
|
J.M. Jowett |
This note shows how to sort
out the large number of beam-beam encounters between the bunch trains in
the LHC into equivalence classes within which bunches see identical sequences
of beam-beam encounters. This makes it easy to produce statistics of the
encounters and to pick out a representative set of bunches for simulation
purposes. |
|
25
|
16 Mar 99 |
VLHC accelerator physics workshop
|
E. Keil |
I took part in the VLHC accelerator
physics workshop on 21 to 25 February 1999 at the Abbey Resort in Fontana
on the shore of Lake Geneva, Wisconsin, USA. It was attended by some 33
people, mostly from FNAL. I was the only person from CERN. The organizers
had hoped for more participants from CERN. The home page of the VLHC study
collaboration at vlhc.org/ is a useful source of information. It will also
have links to the proceedings. FNAL is in the unfortunate position that
it will lose the lead at the energy frontier once the LHC experiments produce
statistically significant results. Therefore, they want their VLHC studies
to be open and visible, and invest funds and manpower. They have great
hopes in their next director, Michael Witherell from UCSB. P. Debenham
DOE took part in the whole workshop. D. Sutter and another fellow from
DOE came for the summary session. Sutter's programme finances part of the
magnet development. He tries to push the field to 20 T. |
|
24
|
15 Mar 99 |
Magnet error tables from Oracle via the WEB
|
E. Wildner |
The magnet error files used
by MAD can be obtained directly from the ORACLE Database via a Web interface.
This is a description of what these files contain and how to generate them
for use by MAD. |
|
23
|
5 Mar 99 |
Constructing Beam-Beam Encounters for the LHC
|
J.M. Jowett |
This note shows how to build
the MAD description of all head-on and parasitic beam-beam encounters of
any bunch in the LHC, taking account of the detailed structure of the bunch
trains, the differences in arc-lengths, orbits and optics between the rings
and the charges of individual bunches. It is based on the calculation of
the collision schedule described in [1] and related technical documents
[2]. Where beam-beam encounters occur inside thick optical elements, these
are split appropriately by an automated sequence-editing operation. This
is a preliminary version: it cannot illustrate the full process until the
optics of Ring 2 is available. All places where modifications are needed
are marked in red. |
|
22
|
1 Mar 99 |
Beam Losses and Collimation in VLHC
|
J.B. Jeanneret, E. Wildner |
This note contains the slides
of a presentation at the VLHC worshop in Wisconsin in February 1999. We
presented LHC data extrapolated to 100 TeV for energy deposition in magnet
coils per proton lost, quench limits, estimated transient and steady losses
and needed collimation performances. A nearly optimum collimation system
is described, with space reservation in dedicated straight sections. We
showed that single diffractive interactions in collision induce critical
losses in the dispersion suppressors near experimental insertions, which
require a local momentum cleaning This would also offer the possibility
to do single diffractive physics not feasible otherwise. Our participation
to the workshop was virtual and we thank N. Mokhov who presented our slides. |
|
21
|
24 Feb 99 |
Collision Schedules for the LHC
|
J.M. Jowett |
This note provides the full
technical background to LHC Project Note 179. It includes an extensive
pedagogical exposition of the collision schedule problem and its solution,
illustrated with simple applications. The nominal filling scheme of the
LHC is treated in detail. Further applications only need to load a small
package file that includes and automatic report generator for alternative
filling schemes. |
|
20
|
11 Feb 99 |
Shielding by a Thin Resistive Layer - Comments
on Beam Physics Note 18
|
F. Caspers, E. Jensen |
We are referring to Beam Physics
Note 18 [1 ], where it is stated that a metallic coating thin compared
to the skin depth is not an effective shield. We believe that this statement
is valid only for infinitely long structures. When considering typical
geometries for LHC kickers, the finite length must not be neglected. The
results for infinitely long structures are correct, but not relevant. With
the help of an example it is shown that the current through the resistive
layer can in fact be dominant, in which case the resistance of this layer
gives a convenient upper bound for the beam impedance. Both numerical simulations
and bench measurements confirm this result. |
|
19
|
5 Feb 99 |
Distribution functions and stability diagrams
with octupoles
|
L. Vos |
A simple procedure is presented
to compute the two-dimensional stability diagram related to tune spreads
arising from octupoles. The excellent agreement with the results in [1]
is somewhat surprising and may be of interest to some of us. |
|
18
|
14 Jan 99 |
Electro-magnetic Shielding
|
L. Vos |
The penetration of electro-magnetic
fields through a metal wall with different layers of dielectric is computed
from basic principles. The results are confronted with those obtained by
B. Zotter [6,7] and A. Piwinski [8] which are very similar. The disagreement
between the two approaches is profound. Engineering practice and tests
in the laboratory confirm the theory of shielding given in this paper.
It is also shown that the interpretation of shielding reported in a recent
paper [3] concerning shields in kickers is not correct. . |
|
17
|
11 Jan 99 |
How the LEP tunnel geometry favours betatron tunes
for LHC
|
J.-P. Koutchouk |
It was shown lately that the
LHC dynamic aperture depends significantly on the integer tunes through
resonances excited by the field uncertainties (systematic per arc. We show
that the layout of the LHC dipoles allowed by the LEP tunnel is such as
to make the 10kth azimuthal harmonics of all multipolar field perturbations
almost vanish. If flexible enough, LEP and LHC optics could take advantage
of this feature to avoid systematic resonances. |
|
16
|
08 Jan 99 |
Longitudinal Space-charge
|
L. Vos |
The transverse space-charge
effect has been treated in [1]. Longitudinal phenomena related to space-charge
in a low energy proton machine have been reported in [2]. Since the transverse
space-charge effect is relevant for the SPS at injection energy it is somewhat
natural to consider also the longitudinal space-charge effect. |
|
15
|
05 Jan 99 |
Phase advance and beam kick cut in a drift space
|
J.-B. Jeanneret |
The best phase advance for
cutting a kicked beam is computed in usual coordinates for those who do
not like, or do not believe, results obtained with normalised coordinates. |
|
14
|
18 Dec 98 |
New 6D beam-beam element in MAD8
|
L.H.A. Leunissen |
A new beam-beam element for
MAD8 is described. |
|
13
|
15 Dec 98 |
The self-field calculation in a relativistic bunch
|
G. Guignard |
This note is related to the
paper "Electromagnetic limitations of an intense charged particle beam"
and the possible space charge limitations due to the current density of
strongly focused beams in high energy accelerators (H. Riege) . It follows
a discussion on the subject (Friday 4th December 1998) and presents one
possible method to deal with the calculation of the longitudinal electric
field on the axis of a single relativistic bunch. Results are given for
a cylindrical bunch of radius a and length lB for both an uniform and a
truncated gaussian charge density. The expression obtained with the uniform
distribution for the field amplitude at the bunch edge differs from the
equation (20) by a factor a/gamma. Since this factor is usually very large
for either the LHC of the CLIC beam, it would strongly modify the conclusions
drawn about the risk of having beam densities close to the Langmuir-Child
limit in future accelerators. |
|
12
|
15 Dec 98 |
Le MAD-9 Nouveau est arrive...
|
C. Iselin |
New features in MAD-9, Version
9-1. |
|
11
|
14 Dec 98 |
Octupoles, Landau damping and feedback: some information
from Fermilab
|
J.M. Jowett |
A summary of information received
from Fermilab about the use of octupoles and feedback. |
|
10
|
26 Nov 98 |
Effects of the sextupoles configuration on the
performance of the (102o, 90o) optics in LEP
|
J.M. Jowett |
The (102o, 90o) optics used
in LEP in 1998 had a new sextupole configuration. This led to a substantial
increase of dynamic aperture. This note summarises the calculations and
illustrates the physics behind this. It also discusses other beam parameters
such as the vertical emittance. |
|
9
|
19 Nov 98 |
LHC Arc Lengths in Version 6
|
J.M. Jowett |
Each ring of the LHC moves
from the outer to the inner aperture of the arc magnets in the experimental
straight sections. The arc-length distance traversed by a particle is greater
in the arcs where it passes through the outer aperture. This Mathematica
notebook derives the arc-length slippages from the MAD description. The
results are used to build a model of the arc-length differences that can
be used to simplify the analysis of the beam-beam collision schedule without
introducing any approximation. |
|
8
|
11 Nov 98 |
Impedance of the ‘rough’ beam pipe
|
M. D'Yachkov |
In order to reduce the reflection
of the synchrotron radiation from the LHC beam screen it has been suggested
to make the surface of the dipole screen rough by placing small ribs along
the screen. In this note we estimate a contribution of the ribs to the
low-frequency beam impedance. |
|
7
|
11 Nov 98 |
Tolerance to broken orbit correctors in the LHC
arcs
|
J.-P. Koutchouk |
There are between 0 and 2 LEP
orbit correctors becoming faulty every week. In LHC the time it would take
to fix them could become significant. The question is therefore raised
as to whether LHC could run with missing orbit correctors or whether some
remote switching between power converters should be implemented. The number
of unknown parameters makes the point rather a problem of judgment. In
this mote I argue that redundancy is not necessary but that the BPM system
is critical. |
|
6
|
6 Nov 98 |
Present situation of the cleaning insertions IR3
and IR7
|
J.-B. Jeanneret, D. Kaltchev, A.
Verdier, |
We analysed and matched many
different optics for the collimation insertions IR3 and IR7 of LHC. In
each insertion only one case emerges which offers good properties for collimation.
This option is also interesting in that sense that it simplifies the hardware
of the dispersion suppressors. |
|
5
|
6 Nov 98 |
Constant Term in the Detuning with Amplitude due
to Sextupole
|
F. Schmidt |
Constant Term in the Detuning
with Amplitude due to Sextupole is discussed. |
|
4
|
27 Oct 98 |
Comparison of LHC Optics Versions 5 and 6
|
J.M. Jowett |
This notebook is a follow-up
from OpticsCheckOut.nb distributed as Beam Physics Note 3. It takes two
similar LHC optics, namely Versions 5 and Version 6, and goes through a
sequence of comparisons. More checks and calculations can be added in the
framework as required; suggestions are welcome. |
|
3
|
27 Oct 98 |
Checks on LHC optics V 6.-2
|
J.M. Jowett |
This document takes an LHC
optics and goes through a sequence of standard checks and validations.
Its content is not meant to be definitive. Its purpose is to provide a
framework in which more checks and calculations on any future version of
the LHC optics can be added as required. Suggestions are welcome. |
|
2
|
2 Nov 98 |
Field in a pill box cavity with thin conducting
layer at r = a
|
G. Dôme |
We consider a perfectly conducting
pill box cavity with a very thin resistive layer much thinner than the
skin depth at the beam pipe radius r=a. The integral equation corresponding
to excitation by a particle beam is derived and discussed, showing that
penetration through the resistive layer takes place only at the resonant
frequencies of the coaxial cavity modes. |
|
1
|
21 Oct 98 |
Beam-beam in LHC
|
J. Gareyte |
Summary of the presentation
on Beam-Beam in LHC at LHC Forum of 13 October 1998. |
