Beam-beam studies for the Tevatron Page: 3 of 12
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to Digital Library by the UNT Libraries Government Documents Department.
The following text was automatically extracted from the image on this page using optical character recognition software:
IP M 0 4 -- ------------- 40
Middle of train __->
0 - 4 _---------- e e . --------e
Figure 3: Schematic of the collision scheme for different
bunches in a train.
Figure 4: Plot of the beta functions around the IP showing
that the optics is anti-symmetric around the IP.
is a three-fold symmetry so there are twelve equivalence
classes of beam-beam kicks. In Run IIb with 140x 105,
there will possibly be one train of proton bunches meeting
two trains of anti-proton bunches. This is required so that
every anti-proton bunch meets a proton bunch at BO and
DO. There is no symmetry in this scenario so there will be
105 different equivalence classes of beam-beam kicks for
the anti-proton beam. Table 1 shows a set of basic parame-
ters for Run IIb. These values are subject to change.
Some of the questions which a study of the beam-beam
interactions must answer include:
* Do the beam-beam interactions with crossing angles ex-
cite significant synchro-betatron resonances?
* Which of the long-range interactions have an important
influence on the beam?
* What is the optimum crossing angle?
* Which of the following effects have an important influ-
ence on the beam?
Static: Transverse coupling, bunch to bunch intensity vari-
ations, unequal emittances, phase advance errors from IP to
Table 1: Basic parameters for Run IIb with a 132 nanosec-
ond bunch spacing. Some of these parameters such as the
number of bunches and crossing angle represent best esti-
mates at present.
IP, chromatic variation in*, ..
Time dependent: Tune modulations and/or fluctuations,
beam offset modulations and/or fluctuations .
* What measures are useful in improving the lifetime? e.g.
resonance compensation, reduction of tune shift with am-
plitude, beam-beam compensation,...
2 BEAM-BEAM INTERACTIONS WITH
A CROSSING ANGLE
The impact of all the beam-beam interactions with Run IIb
parameters requires a detailed study before we will know
if the beams are sufficiently stable. As a start we have be-
gun investigations of the effect of the synchro-betatron res-
onances excited by the crossing angle at the main IPs. In
this section I will report on our simulation studies with a
Figure 5 shows the simulation model for treating the
beam-beam interactions at a crossing angle. This model
has the following features:
* 6D interactions at BO and DO. This includes the change
in energy from the beam-beam interaction.
* Strong beam bunch (protons) is sliced into 9 disks to
account for the crossing angle. The transverse distance
of the anti-proton from the center of each disk is used
to calculate the beam-beam kick from that disk and then
the kicks are summed over all disks. All of these kicks
are delivered at the same instant so the anti-proton is not
propagated from disk to disk.
* Transverse size of the disks increases away from the IP.
This takes into account the hourglass effect.
* Equal crossing angles in both planes - the crossing plane
Number of bunches (p x p)
NP per bunch
NP per bunch
Bunch separation [nsec]
u* (p/p) [pm]
uS (p/P) [cm]
Half crossing angle 0 [prad]
Beam-beam tune shift - 2IPs (p/p)
Piwinski parameter (u8/*) [prad]
No. of long-range interactions
14.0 x 10u
~140 x 105
2.7 x 1011
3 x 1010
3.15 x 1012
(0.77/6.0) x 10-3
Here’s what’s next.
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Sen, Tanaji. Beam-beam studies for the Tevatron, article, June 13, 2000; Batavia, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc710905/m1/3/: accessed April 24, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.