IR Design Status and Update

IR Design Status and Update M. Sullivan For M. Boscolo, K. Bertsche, E. Paoloni, S. Bettoni, P. Raimondi, M. Biagini, P. Vobly, I. Okunev, A. Novokhatski, S. Weathersby, et al. SuperB General Meeting XV Caltech, Pasadena, Calif. December 13-17, 2010

Outline • IR design • Quick recap of the IR design • SR Backgrounds • Anatomy of programs • SYNC_BKG (QSRAD) • MASKING (EGS4) • Generating high statistics • SR calculations • Power • Rates • Summary and Conclusions

Present Parameters (V12 lattice)

Parameters used in the IR designs Parameter HER LER Energy (GeV) 6.70 4.18 Current (A) 1.89 2.45 Beta X* (mm 26 32 Beta Y* (mm 0.253 0.205 Emittance X (nm-rad) 2.00 2.46 Emittance Y (pm-rad) 5.0 6.15 Sigma X (m) 7.21 8.87 Sigma Y (nm) 36 36 Crossing angle (mrad) +/- 30

General IR Design Features • Crossing angle is +/- 30 mrads • Cryostat has a complete warm bore • Both QD0 and QF1 are super-conducting • PM in front of QD0 • Soft upstream bend magnets • Further reduces SR power in IP area • BSC to 30 in X and 100 in Y (7 fully coupled) • SR scanned to 20 in X and 45 in Y

Details of the permanent magnet slices • Z from IP Len. R1 R2 G • Name Beam m cm mm mm T/cm • QDPA LER 0.30 1 7.5 12.5 1.392 • QDPB LER 0.31 1 7.5 13.0 1.473 • QDPC LER 0.32 1 7.5 13.5 1.547 • QDPD LER 0.33 1 7.5 14.0 1.616 • QDPE LER 0.34 1 7.5 14.5 1.680 • QDPF LER 0.35 1 7.5 15.0 1.740 • QDPG LER 0.36 1 7.5 15.5 1.796 • QPDH drift 0.37 1 • QDPI HER 0.38 1 7.5 16.5 1.899 • QDPJ HER 0.39 1 7.5 17.0 1.945 • QDPK HER 0.40 1 7.5 17.5 1.989 • QDPL HER 0.41 1 7.5 18.0 2.030 • QDPM HER 0.42 1 7.5 18.5 2.070 • QDPN HER 0.43 1 7.5 19.0 2.107 • QDPO HER 0.44 1 7.5 19.5 2.142 • QDPP HER 0.45 1 7.5 20.0 2.175 • QDPQ HER 0.46 1 7.5 20.5 2.207 • QPDR HER 0.47 1 7.5 21.0 2.238 • QDPS HER 0.48 1 7.5 21.5 2.266

Vanadium Permendur Design • We allow for 3 mm of space for the coils (new information from Ivan – actually 2.6 mm) • The central steel section can be very thin because the magnetic field in the steel is nearly cancelled from the twin windings • The QD0 magnet is aligned as much as possible to the beam axis, however we must slant it with respect to the beam axis in order to accommodate the increasing horizontal size of the beam-stay-clear

Vanadium Permendur “Russian” Design

VP design details • PM as described earlier • Magnet QD0 QD0H QF1 QF1H • IP face (m) 0.55 0.90 1.25 1.70 • Length (m) 0.30 0.15 0.40 0.25 • Angle wrt beam (mrad) 13.33 0 2 1 • G (T/cm) 0.956 0.706 0.408 0.381 • Steel aperture (mm) 40 50 74 78 • Max. Field (T) 1.91 1.77 1.51 1.49

Air-Core “Italian” Design • We replace the shared QD0 and QF1 parts of the VP design with the air-core design • Also place QD0 and QF1 parallel to the detector axis • Then we have the same field strengths and the LER and HER pieces are the same strength as the VP design

Air core “Italian” QD0, QF1

AC design details • PM as described above • Magnet QD0 QD0H QF1 QF1H • IP face (m) 0.55 0.90 1.25 1.70 • Length (m) 0.30 0.15 0.40 0.25 • Axis offsets (mm) 0.5 --- 4 --- • Angle wrt beam (mrad) 30 0 27 1 • G (T/cm) 0.956 0.706 0.408 0.381 • Aperture (mm) 35 50 73 78 • Max. Field (T) 1.67 1.77 1.49 1.49

SR backgrounds • No photons strike the physics window • We trace the beam out to 20 X and 45 Y • The physics window is defined as +/-4 cm for a 1 cm radius beam pipe • Photons from particles at high beam sigmas presently strike 7-10 cm downstream of the IP • However, the highest rate on the detector beam pipe comes from points that are a little farther away • This is true for both the vanadium permendur and the air-core design

SYNC_BKG • Originally QSRAD (by Al Clark of LBL) • Histograms the critical energies of the SR fans • Very fast – A setup with as many as 60 masks, 30 magnets and a 20 by 45 beam scan in 0.1 steps takes seconds to run on a 7 yr old laptop • This allows for rapid masking design changes or for various beam profile runs • Enhancements • Second gaussian beam tail distribution • Offsets and tilts to magnets (Stan Hertzbach of UMass) • Parametrization of the energy spectrum • Series of falling exponentials over the energy range • This function is easily transferred over to the EGS4 program for efficient photon generation

VP SR photon hits/bunch (>4 keV) LER HER 8.1E6 2.5E6 7.1E4 6.5E5 1.1E8 3.8E6 0 5.4E7 3.0E4 0 SB_SF10A_7_A.LIS SB_SF10A_4_A.LIS

Output from SYNC_BKG for the HER Source of photons that hit 7 cm from the IP IP

Where in the beam profile Vertical beam sigmas Horizontal beam sigmas

Surface 10 cm from the IP Source of photons that hit 10 cm from the IP

Where in the beam profile

Source for the septum photons

Where in the beam profile

Masking • EGS4 interface program to track photons that strike a beam pipe surface using input from SYNC_BKG • Fast – 108 photons takes about 2.5 min. on a 7 yr. old laptop – present code limit is 2x109 photons for a single run • Some features • Several photon energy spectra options • Twenty different materials with at least 10 layers possible • Reflection / transmission / absorption • Any angle of incidence to surface • Surface can have an edge • Surface can have a radial tip • Reflected photons can be tracked for possible hit on the inside of a cylinder surface (detector beam pipe) • Reflected (or transmitted) photons can be saved as input to another MASKING run (photon files can be added)

Hits/bunch incident on and through (n) the detector beam pipe from the HER Using a conservative beam tail LER HER 51 (4.2) 47 (12) 201 (2.6) 113 (6.3) Beam pipe has 3 m Au SB_SF10A_7_A series

SR power (VP design) 115 52 8 295 56 17 42 32 390 205

SR power (AC design) 115 57 8 311 57 17 43 35 402 215

SR power that strikes beam pipe inside the cryostats • We can now model the SR power that strikes the beam pipe inside the cryostats and find how much power penetrates the pipe • The most difficult part to control is the section of beam pipe inside the QD0 • We may find that we will need to coat the inside of the beam pipe with Au or other high Z material in order to increase the x-ray absorption

First few runs looking at QD0 • Tried three cases • Attenuation • 1 mm Cu 3.0x10-2 • Power (W) 6.45 • 10um Au and 1 mm Cu 1.4x10-2 • Power (W) 3.01 • 1 mm Au 2.2x10-5 • Power (W) 0.005

Summary (1) • We have dusted off the MASKING program and gotten it to run on a PC • We have run one of the IR designs (vanadium permendur) for the HER to get the number of photons/crossing that strike and penetrate the detector beam pipe from photons reflected from nearby surfaces • The HER generates almost all of the SR background for the SVT and the two designs (vanadium permendur and air core) are very similar • The background rates are very similar to the rates seen in the BaBar design (few photons per crossing)

Summary (2) • With the MASKING program working again we can study various parameters that control the background rates • We have found that the SR rates are dominated by the hits on the beam pipe just downstream of the physics window (no surprise) • The thickness of the Au layer on the inside of the pipe ranging from 3-10 m changes the background rate by about a factor of 2-3 (again, no surprise) • The high incident photon rate on the septum is compensated by the small solid angle to the detector beampipe to such an extent that this source is smaller than the nearby sources (small angle of incidence on the detector beampipe also helps)

Summary (3) • We have taken a first look at the power going into the cryostat in QD0 • 1 mm of Cu may be too thin (6W) • 10 um of Au helps (factor of two) • 1 mm of gold looks very good (Ta should also work as well)

Conclusion • We now have a suite of programs that allows one to do rapid proto-typing on the design • This will allow us to optimize the design for maximum SR background control

IR Design Status and Update