11 Overview of the Tevatron Collider V.S. Morozov Old Dominion University Muons, Inc. Collider Review Retreat, Jefferson Lab, February 24, 2010

2 Outline Accelerator Complex Overview Tevatron Low-  insertion Electrostatic p/p beam separators 1 st - and 2 nd -order chromaticity control Beam-beam effects Instabilities ¯

f 30 September 2002Elvin Harms - HCP Accelerator Complex Overview

f 4 –Proton source Cockroft-Walton preaccelerator 750 keV

f 5 Accelerator Complex Overview –Proton source Drift tube Linac 116 MeV –Proton source Side-coupled cavity Linac 400 MeV

f 6 Accelerator Complex Overview –Proton source Rapid-cycling Booster synchrotron 8 GeV

f 7 Accelerator Complex Overview Main Injector/Recycler 8 to 150 GeV

f 8 Accelerator Complex Overview Antiproton source –Antiproton production target station 120 GeV –Debuncher 8 GeV –Accumulator  8 GeV

f 9 Accelerator Complex Overview Tevatron –Superconducting synchrotron 980 GeV

f Elvin Harms10 Tevatron Loading scheme Protons are loaded first - 1 bunch at a time and spaced in 3 groups of 12 (20 empty buckets between bunches, 139 empty buckets between trains) Antiprotons are loaded four bunches at a time for a total of 9 transfers from the Accumulator to MI to the Tevatron The 36 bunches of Pbars are equally spaced in 3 groups of 12 around the Tevatron

November 8, 2002 Fermilab Snapback Workshop Mike Martens 11 Tevatron Parameters Synchrotron with superconducting magnets. Collide 36 proton bunches on 36 pbar bunches. Radius 1 km Energy 150 Gev to 980 Gev Lattice 6 identical 60º arcs with 15 FODO cells/arc FODO cell  min = 30 m,  max = 100 m, ~60º betatron phase advance in both planes Run with tunes at (vertical) and (horizontal). h 1113 RF frequency MHz Bucket spacing 18.8 nsec Low Beta regions at B0 and D0.  * is 35 cm Electrostatic separators to separate the proton and antiproton orbits. 772 dipole magnets with B = GeV.

f 30 September 2002Elvin Harms - HCP Parameter List RUNIb ( ) 6 x 6 Run IIa (36 x 36) Current best Protons/bunch2.3 x x Antiprotons/bunch0.55 x x Total Antiprotons3.3 x Pbar Production Rate6.0 x /hour Proton Emittance 23  mm-mrad20  20  mm-mrad Antiproton Emittance 13  mm-mrad15  20  mm-mrad ** 35 cm3535 cm Energy900 GeV Bunch Length (rms)0.60 meter0.37~0.60 m Crossing Angle 0  rad 00 Typical Luminosity1.6 x cm -2 s best-to-date Integrated Luminosity3.2 pb -1 /week Bunch spacing~3500 nsec396 Interactions/Crossing2.52.3

13 Ingredients of Tevatron Luminosity Low-  insertions Reduction of beam-beam tune shift by separation of p and p beams on helical orbits Control of 1 st and 2 nd -order chromaticities ¯

14 Retrospective View Talk by R. Johnson, ~1986

November 8, 2002 Fermilab Snapback Workshop Mike Martens 15 Standard Cell in the Tevatron Lattice FD Tevatron Dipole F Tevatron Quadrupole Tevatron Quad corrector Tevatron Sextupole corrector Tevatron Beam Position Monitor T:QF T:SF Horz BPM T:QD T:SD Vert BPM (There are 772 Tevatron dipoles)

16 Low-  Insertion Two low-  insertions at B0 and D0 18 cold-iron quads arranged as a triplet and 6 “trims” on each side of interaction region Fully matched to lattice by “trims” Approximately symmetric around interaction point Magnetic gradients antisymmetric Each insertion’s  * independently adjustable within m range

17 Low-  Insertion Each insertion adds half unit to betatron tunes Horizontal dispersion zero at interaction point  * limited by  max, magnet’s bore tube and field errors Inner quads specially designed to fit detector clearance

18 Low-  Insertion  * of 35 cm prior to 2005 New optics with  * of 28 cm implemented in July 2005 based on precise knowledge of lattice details obtained using Orbit Response Matrix (ORM) and Linear Optics from Closed Orbit (LOCO) methods Gain in luminosity of ~10% Further reduction of  * undesirable because of 2 nd -order chromaticity and hour-glass effect

November 8, 2002 Fermilab Snapback Workshop Mike Martens 19 Tevatron Ramp Cycle Time Tev Energy 980 Gev flattop 150 Gev Front Porch 90 Gev Reset Low beta Squeeze 150 Gev Back porch Typical times for Tevatron store 150 Gev Front porch: ~2 hours 980 Gev Flattop: ~12-24 hours 150 Gev Back Porch: ~1 minute 90 Gev Reset: ~20 seconds Low beta Un-squeeze Typical times for dry squeeze 150 Gev Front porch: ~10 minutes 980 Gev Flattop: ~15 minutes 150 Gev Back Porch: ~1 minute 90 Gev Reset: ~20 seconds Inject porotns & pbars During injection and acceleration  * kept at 1.7 m then “squeezed” to 0.28 m by ramping trim magnets while triplet elements remain unchanged In fixed target runs low-  insertions approximate “normal-  ” straight sections

20 Separation of Proton and Antiproton Orbits Tevatron’s betatron tune working point between 4/7 and 3/5 resonance lines leaving tune space available Beam-beam tune shift for antiprotons and 0.02 for protons Unseparated beams  multiple crossing locations each contributing to beam-beam tune shift  limited number of bunches and beam intensity Keep beams separate everywhere except interaction regions with electro-static separators

21 Electro-Static Separators Function as “3-bumps” in vertical and horizontal planes Bunches go in helical orbits around unseparated orbit Orbits remain separated during injection and acceleration Separators adjusted to bring beams into collision at interaction regions

22 Electrostatic Separators 1986 talk by R. Johnson1991 paper by D. Herrup et al.

November 8, 2002 Fermilab Snapback Workshop Mike Martens 23 Chromaticity in the Tevatron High chromaticity -large betatron tune spread -some beam loss on ramp (~15%). Reducing chromaticity ma cause transverse instabilities Keep chromaticities at 8 units (horz and vert) on front porch Increase chromaticites to 12 units just before ramp. Keep chromaticity at 15 to 20 units on the ramp. Chromaticity drifts are created by drifting b2 (sextupole) fields in dipoles. b2 compensation scheme keeps chromaticity constant at 150 Gev and on the snapback (sort of.)

November 8, 2002 Fermilab Snapback Workshop Mike Martens 24 Chromaticity in the Tevatron The total chromaticity has several components  Total =  Natural +  Dipoles +  Sext corr  Natural = -29 units (from optics calculations)  Dipoles =  b2 drift +  b2 geometric  Sext corr =  T:SF +  T:SD +  C:SFB2 +  T:SDB2 176 chromaticity correction sextupoles Originally combined into two families, SF and SD 88 elements in each family powered in series Sextupoles located next to quadrupoles of regular FODO lattice

25 Transverse Dampers Lower chromaticity by 4-6 units thus reducing betatron tune spread and improving beam lifetime Use transverse dampers to keep beam stable

26 2 nd -Order Chromaticity Correction Needed to move betatron tune working point to new place near 1/2 resonance where there is more tune space available Elimination of chromatic dependence of beta function at IP should improve beam lifetime

27 2 nd -Order Chromaticity Correction Sextupoles with  or  /2 betatron phase advance with respect to final focus quads were identified 22 sextupoles were taken out from each of SF and SD families They were grouped into 4 families New groups allow one to change 2 nd -order chromaticity while keeping linear chromaticity constant

28 2 nd -Order Chromaticity Correction 2 nd -order chromaticity reduced from to units

f 29 Beam-Beam Effects – 150 GeV IssueSolutionImpact on LuminositySchedule Increased Proton IntensityTransverse Dampers30% to L 0 Horizontal commissioning in progress, vertical to follow (this month) Improve injection aperture and emittance growth Improved MI to Tevatron transfer line match 6% to L 0 Matching in progress Improve injection aperture and emittance growth Turn-by-turn position diagnostics and orbit closure algorithm 6% to L 0 Pbar system in operation Improve injection aperture and emittance growth Fast injection dampers5-10% to L 0 Early 2003 Limited aperture and separation at 150 GeV Replace C0 Lambertson magnets with larger aperture dipoles (double the vertical aperture) 10% to L 0 Next extended shutdown Limited aperture and separation at 150 GeV Improved optics across A0 straight section 5-10% to L 0 Early 2003 Time-dependent tune and coupling drift at 150 GeV Tune drift compensation2-5% on integrated LPut into operation last week

f 30 Beam-Beam Effects – 980 GeV IssueSolutionImpact on LuminositySchedule Drifting tunes during storeOn-line tune stabilization 4-10% in integrated Luminosity Long-term Low lifetime – restore to Run I values (>15 hours) Explore larger helix separation 10-30% in integrated Luminosity Long-term Low lifetime – restore to Run I values (>15 hours) Optimize tunes for most bunches up to 30% in integrated Luminosity Long-term Pbar tune shift by protonsBeam-beam compensation with electron lens 10% in integrated Luminosity Long-term

f 31 Instabilities IssueSolutionImpact on LuminositySchedule Coherent transverse beam blow-up at all beam energies Transverse dampers, additional investigation see aboveDamper commissioning in progress Coherent longitudinal bunch by bunch beam blow- up Longitudinal bunch-bunch dampers, additional investigation better understandingLongitudinal damper in operation at 150 and 980 GeV Coherent ‘dancing bunches’Observed, under studybetter understandingDecember 2002 Incoherent bunch length growth Observed, under studybetter understandingearly 2003

talk by R. Johnson2006 paper by A. Valishev