IR Optimization, DID and anti-DID Page: 1 of 5
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IR OPTIMIZATION, DID AND ANTI-DID*
Andrei Seryi, Takashi Maruyama, SLAC, Stanford, CA, USA
Brett Parker, BNL, Upton, NY 11973, USA.
In this paper, we discuss optimization of the larger
crossing angle Interaction Region of the Linear Collider,
where specially shaped transverse field of the Detector
Integrated Dipole can be reversed and adjusted to
optimize trajectories of the low energy pairs, so that their
majority would be directed into the extraction exit hole.
This decreases the backscattering and makes background
in 14mrad IR to be similar to background in 2mrad IR.
In the machines with crossing angle, the detector
solenoid field results in a deviation of the vertical
trajectory and in a small vertical angle at the IP (about
100 grad for crossing angle of 20mrad). This angle is anti-
symmetrical for e+e- machines and does not affect the
luminosity. The vertical angle at the IP also causes
rotation of the spin by about a degree resulting in a
misalignment of the spin orientation at the IP with respect
to the upstream polarimeter. The Detector Integrated
Dipole (DID) is a pair of coils wound on the detector
solenoid which creates sine-like transverse field, giving
the possibility to adjust the beam trajectories near the
interaction region . The DID was originally suggested
as a way to compensate the vertical angle at the IP, as
illustrated in Fig. 1, and avoid spin misalignment.
fields acting in Y
t 0.02 - Total
Pairs at z 3.51 m
Figure 2: Distribution of pairs at 3.5m from IP in SiD
detector when DID is used to compensate the vertical IP
angle of the incoming beam. The incoming and outgoing
apertures are shown by magenta and green colors.
- +'+""' -.
-10 -8 -6 -4 -2 0
-61 IFigure 3: Trajectories of pairs coming from the IP in SiD
-10 -8 -6 -4 -2 Z, m 0 detector when DID is used to compensate the vertical IP
gure 1: Compensation of the incoming beam vertical angle of the incoming beam. The high energy pairs follow
le at the IP with DID and dipole corrector of the QDO the beam axis (green dashed line) while the low energy
drupole. Field acting in Y (top) and vertical trajectory pairs spiral around the field line (red dashed line).
tom). SiD detector, crossing angle 20mrad, IP at z=0. Large spread of the pairs on the face of BEAMCAL
e DID field creates U-like distortion of the central resulted in backscattering and increase of background
line of the detector solenoid, and compensation of photon hits in TPC (Time Projection Chamber). The
vertical angle of the incoming beam is in fact number of photon hits in TPC increased several times and
valent to aligning the field line, effectively, with the the effect was especially dramatic when the outgoing
ming beam. This increases the transverse field seen aperture was not optimized .
he outgoing beam, in particular the beamstrahlung The technology of compact direct wind SC magnets
. The high energy pairs continue along the initial allows reducing the crossing angle to 14mrad . With
:tion of the beam, while the low energy pairs spiral reduced crossing angle, the synchrotron radiation (SR)
nd the field line and disperse, as shown in Figs.2-3. effects significantly decreased (Asr~Oc512), simplifying
use of reversed DID (anti-DID) described below.
k supported by US DOE, contract number DE-AC02-76SF00515
Contributed to 36th ICFA Advanced Beam Dynamics Workshop (NANOBEAM 2005),
17-21 Oct 2005, Kyoto, Japan
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Seryi, Andrei; Maruyama, Takashi; /SLAC; Parker, Brett & /Brookhaven. IR Optimization, DID and anti-DID, article, February 3, 2006; [Menlo Park, California]. (digital.library.unt.edu/ark:/67531/metadc878368/m1/1/: accessed January 20, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.