Crab-Waist experiment results The 40th ICFA Advanced Beam Dynamics Workshop on High Luminosity e + e – Factories, April 14–16, 2008 Budker Institute of Nuclear Physics, Novosibirsk Catia Milardi for the DA  NE Commissioning Team (*) (*) David Alesini, Maria Enrica Biagini, Caterina Biscari, Roberto Boni, Manuela Boscolo, Fabio Bossi, Bruno Buonomo, Alberto Clozza, Giovanni Delle Monache, Theo Demma, Enrico Di Pasquale, Giampiero Di Pirro, Alessandro Drago, Alessandro Gallo, Andrea Ghigo, Susanna Guiducci, Carlo Ligi, Fabio Marcellini, Giovanni Mazzitelli, Catia Milardi, Fabrizio Murtas, Luigi Pellegrino, Miro Preger, Lina Quintieri, Pantaleo Raimondi, Ruggero Ricci, Ugo Rotundo, Claudio Sanelli, Mario Serio, Francesco Sgamma, Bruno Spataro, Alessandro Stecchi, Angelo Stella, Sandro Tomassini, Cristina Vaccarezza, Mikhail Zobov (INFN/LNF, Frascati (Roma)), Ivan Koop, Evgeny Levichev, Pavel Piminov, Dmitry Shatilov (BINP SB RAS, Novosibirsk), Victor Smaluk (BINP, Novosibirsk), Simona Bettoni (CERN, Geneva), Marco Schioppa (INFN Gruppo di Cosenza, Arcavacata di Rende (Cosenza)), Paolo Valente (INFN-Roma, Roma), Kazuhito Ohmi (KEK, Ibaraki), Nicolas Arnaud, Dominique Breton, Patrick Roudeau, Achille Stocchi, Alessandro Variola, Benoit Francis Viaud (LAL, Orsay), Marco Esposito (Rome University La Sapienza, Roma), Eugenio Paoloni (University of Pisa and INFN, Pisa), Paolo Branchini (Roma3, Rome)

Outline Short overview about the new collision scheme and collider upgrade: Large Piwinski angle and crab-waist New IR1 New Ring Cross Region (RCR) replacing former IR2 New injection kickers New bellows Some crab-waist related issues from the DA  NE commissioning: Vacuum Ring optics Orbit correction & beam based alignment Betatron coupling correction Beam currents Bunch length and ring impedance New collision scheme test Luminosity measurements Background Conclusions, open points and plans

Large Piwinski angle  obtained by: smaller  x larger  Small  y * in fact the beams overlap region  is: Crab-Waist transformation Collision scheme with large Piwinski angle and Crab Waist L geometric gain low  x L geometric gain low  y lower  y (  y ~  z ) Y synchro-betatron resonance suppression L geometric gain X-Y synchro-betatron and betatron resonance suppression sextupole(anti)sextupole IP New IR layout Lower beam  High colliding currents New low-  section Ad hoc ring optics Powerful SXTs Ring optics requirements

Beam Beam Long Range interaction almost cancelled 1PC ->  x PC ~20  x IR1 Evolution splitter magnets and compensator solenoids removed large collision angle ~ 50 mrd low-beta section based on Permanent Magnet QUADs: K QD = [T/m] k QF = 12.6 [T/m] e + e - vacuum chambers separate after the Q D four C type corrector dipole are used to mach the vacuum chamber in the arc Aluminum vacuum chamber Thin window thickness= 0.3 mm 0.54 m

Splitter magnets and compensator solenoids removed Geometrical layout symmetric to the IR1 “Half Moon” vacuum chamber: provides full beam separation designed to fit inside the existing EM quadrupoles can be easily replaced by an IR RCR Ring Crossing Region No BBLR interaction contribution from RCR

New injection KICKERS test 25 kV 200 ns 45 kV 6 ns  The new kickers are powered by new pulsed power supply (6 ns pulse length), and they are also compatible with the old pulsers (200 nspulse length)  First test on e+ ring with fast pulsers have been successfully done.  Unfortunately we had problems with the new fast FID pulsers after few hours of operation. They have been now recovered and ready to be re-installed. New stripline kicker providing better deflecting field uniformity

NEW BELLOWS 6 new bellows for each ring; Shielding based on Be-Cu  strips 0.2 mm thickness; lower impedance and improved mechanical specifications; OLD BELLOW

DA  NE commissioning milestones Commissioning started at the end of November Both beams stored in the first days of December January low-beta optics applied First week of February solenoid winding installed in the MRp 800 mA e + current stored for the first time after the upgrade (pattern not suitable for collisions) February Crab-Waist sextupoles in operation February the 11 th Luminosity monitor installation Beginning of March first L ~ cm -2 s -1 measured March the 10 th SIDDHARTA installation First half of March new transverse horizontal feedback installed in the MRe ring, End of March relevant background reduction in the kaon trigger, transverse and longitudinal feedbacks tuning 900 mA e + current stored in collision, L peak ~ 2*10 32 cm -2 s -1 measured.

Vacuum in the Main Rings 80% of vacuum conditioning by mid february Accumulated dose nowaday: e - ~ 300 A/h e + ~ 200 A/h vacuum leakage detected and partially recovered in the MRe RF cavity Recently measurements pointed out a vacuum contribution from gas bremsstrahlung  SLM  y = > 0.23 Single beam I - ~ 500 mA Dynamic vacuum still needs to be improved

e + currents in the first two months of commissioning the positron current was limited to ~ 400 mA Solenoid windings have been installed in long section of the IR1 and Ring Crossing Region (RCR) during the Feb. 4÷6 shutdown B sol ~ 45 Gauss I + ~ 800 mA stored in 120 contiguous bunches, stable current vacuum limited  + ~ 550 s. Additional solenoids installed in the long straight section gave no further improvement in terms of maximum I +.

Solenoid OFF Solenoid ON

I + ~ 800 mA has been stored in 110 bunches by: Halving the residual orbit oscillation due to the injection kickers by using the transverse horizontal feedback front-end as a diagnostic tool Tuning the feedback systems

Optics Evolution DA  NE operation restarted at the end of November relying on a detuned optics, with x slightly above 5, y above 4 and Crab SXTs off, in order to speed up beam injection, to put the diagnostic in operation and to optimize the optics model. On January, once a reliable machine model had been defined, the ring optics has been moved toward the nominal one having both tunes above 5. Transverse betatron coupling has been corrected mainly by rotating the permanent magnet focusing QUADs in the IR1. The optimum obtained is now  ~.4% in both rings. At the end of January the PM QUAD positions have been optimized and 2 electromagnetic QUADs have been added symmetrically with respect to the IP1 in order to meet the phase advance requirements imposed by the Crab-Waist collision scheme.

Begin of February first collision test with Crab SXTs on. On March 10 th the Crab Sextupole position are moved toward the IP1 On March 16 th the optics in the Ring Crossing Region (RCR) is modified in order to improve the beam stay clear, the external triplet QUADs are moved toward the central one (+35 cm) and the vacuum pipe & QUADs are realigned. On the second half of March two sector dipoles in the MRe are modified and realigned to improve beam acceptance …. still about Optics Evolution

Present SIDDHARTA Optics IR1RCR

Non-linear Optics (sextupoles on)

e +  y has been considerably reduced by: global orbit correction centering the beam vertical orbit in the arc Sextupoles  y MAX ~ 10 cm e -  y optimized by global orbit correction e + before e + after yy xx xx yy Vertical dispersion correction

e - bunch length measurement 20% bunch length I bunch ~ 10 mA due to: ICE removal New injection kickers New bellows Bunch length [cm]

e + bunch length measurement Few % reduction in bunch length due to: New injection kickers New bellows Bunch length [cm]

K s= 38.9 m -2 more than a factor 5 larger than the average required for the normal sextupoles used for chromaticity correction CRAB Sextupoles

CRAB Sextupoles & Beam sizes (on electron beam) Crab off Crab On Beam lifetime is not affected by the CRAB Sextupoles

Luminosity monitors (colliding beams) Crab off Crab On

Hourglass factor Vertical beam-beam scan  x * =.2 mm  y (KEK) =.3 mm  y (PEP) >.4 mm Measured  y is compatible with the value obtained by using the coupling  value (  measured at the SLM

IP LAYOUT AND LUMINOSITY MONITORS SIDDHARTA K monitor Bhabha calorimeter  monitor GEM Bhabha Monitor

Small angle Bhabha tile calorimeter First tile sample delivered BTF test planed for this month 10 sectors per side (30 0 each) made up by alternating lead and scintillator tiles vertical acceptance ÷ X 0 15% 510 MeV

LUMINOSITY PERFORMANCES Specific Luminosity is 3÷4 times higher than during the past best runs, as expected.     exhibit a linear behaviour 109 colliding bunches Achieved 1200mA e - and 850mA e + in collision, L max simultaneous about 700mA against 700 mA

HIGH CURRENT OPERATION 1 day integrated luminosity (7 Apr 08) 90 colliding bunches Luminosity monitors  monitors Bhabha calorimeter Geometrical luminosity evaluation K monitor Within <20% all monitors gives consistent results in term of luminosity Colliding beams Not colliding beams (vertical separation)

8 April bunches in collision Machine performances evolve day by day ….. 90 bunches operations help to keep under control   y blow-up due to the dynamic vacuum conditions

Coupling correction Rotating the permanent magnet quadrupoles in the IR1 Powering skew quadrupoles Tuning transverse vertical feedback gain Colliding beams

Background optimization Background has been optimized by adjusting: Beam orbit Scrapers position Beam acceptance Additional shielding especially in the IR1 Tuning the colliding beam positions in the RCR and IR1:  x + 2mm for both beams (RCR) The total background seems to be strongly dominated by the beams parameter in the RCR Still the background rate must be reduced by a factor 5 to fit the requirements imposed by the SIDDHARTA experiment.

-Operation with crab sextupoles gave the expected results (tested up to 50% of nominal strenght); -Collisions are no longer affected by Beam Beam Long Range interaction; -Ring optics model reliable; -Good vacuum conditioning; -Bunch lengths measurements show a shorter bunch due to lower machine impedance; -Fast kickers successfully test done  we need to go in continuous operation with the new pulsers; -New bellows work; -Achievements: Bunch length ~ mA Current in collision 1200 mA e - and 960 mA e + Transverse betatron coupling k ~ 0.4% measured  IP1 ~ 4  m peak luminosity L peak = 2   ~25% better than the past DA  NE record ( ) Conclusions

-two months delay on the Commissioning schedule; -still peak and integrated luminosity have to be increased; -Beam lifetimes need dynamics aperture optimization; -Background needs to be further optimezed to allow kaonic Deuterium measurements; -No “hard to fix” problems found so far despite the DAFNE collider has been deeply modified. Open Points