of secondary light ion beams NA61 summary of the 2010 test of secondary light ion beams MG, CERN, December 6, 2010 Test goals NA61 test set-up Results Conclusions

Test goals Test production of secondary light (B, C) ion beams at the CERN SPS (13A-158A GeV/c) needed for the NA61 physics Production of primary ion beams needed by NA61 is possible technically, but is significantly (several years) delayed due to a schedule conflict with the LHC Thus, secondary ion beams are very crucial for a timely execution of the NA61 program

NA61/SHINE at the CERN SPS Ion program of NA61/SHINE at the CERN SPS Physics goals: -search for the Critical Point of strongly interacting matter -study properties of the Onset of Deconfinement Experimental strategy: -first two dimensional scan in collision energy and size of the colliding nuclei Detector: -large acceptance hadron spectrometer, upgraded NA49 facility Beams and energies: -secondary beams: p and B at 10A, 20A, 30A, 40A, 80A, 158A GeV -primary beams: Ar and Xe at 10A, 20A, 30A, 40A, 80A, 158A GeV

Progress and plans in data taking for CP&OD Pb+Pb NA49 (1996-2002) Au+Au STAR (2008-10) NA61 ion program Xe+La 2014 Ar+Ca 2012 B+C T T T 2010/11(13) p+p p+p 158 2009/10 p+Pb 2011/12 13 20 30 40 80 158 energy (A GeV) T -test of secondary ion beams

Study the onset of deconfinement and Search for the critical point strongly interacting matter water Temperature (MeV) Baryochemical potential (MeV) critical point 1st order phase transition

Search for the onset of the horn in collisions of light nuclei Study the onset of deconfinement ? 10 20 30 40 80 158 energy (A GeV) Search for the onset of the horn in collisions of light nuclei

T µB Search for the critical point energy A Critical Point: freeze-out close to critical point, and system large enough, expected signal: a hill in fluctuations T energy Pb+Pb A µB

Secondary ion beam: basic idea H2 and NA61 test set-ups Secondary ion beam: basic idea Pb primary Pb beam from the SPS fragmentation target Pb fragments fragment separator

Secondary in beam: fragment separator The beam line is a double spectrometer with 0.04% resolution that helps to separate the ion fragments corresponding to a selected magnetic rigidity : B Target length optimized to fragment production, degrader with variable length – optimization to be determined from the tests Be 18 cm Cu 4 cm 500 m

Secondary in beam: NA61 beam test set-up Z-DET BPD-1 BPD-1 BPD-2 BPD-3 150 m S1 and S2 - scintillators for ion charge measurements A – scintillator for ion charge and mass measurements BPD – Beam Position Detectors (proportional chambers) Z – prototype of the charge trigger detector (Cherenkov: problems with radiator discovered)

Results Pb beams at 13.9A and 80A GeV/c for FT are set-up First attempts to get 80A GeV/c Pb beam in SPS Real time: several days

Test of different injections schemes and debunching were performed Nine injections One injections NA61 count on S1 per spill: 157k NA61 count on S1 per spill: 16k The NA61 rate scales approximately in proportion to the number of injections

Beam intensity is spill is strongly non-flat 13A GeV/c 80A GeV/c

Beam time structure around NA61 trigger After-pulses, rejected in the analysis

Number of beam particles surrounding a trigger particle within a given time window Scaled from 50k to 500k particles per spill on S1 A large (about 50%) of all triggered events have another beam particle within a several micro-seconds window. Flatter and longer spills are needed (a single injection cycle should significantly help)

Optimization of Pb beam on the T2 target Initial Pb beam profiles at the T2 target Horizontal Pb beam profile Vertical Pb beam profile The T2 target thickness: 2 mm After optimization the maximum beam intensity in NA61 increased by a factor of several We hope that the width of the beam at the T2 target can be still decreased and/or the target thickness increased

Tests of secondary light ion beams 80A GeV/c beams were delivered to NA61 only for several hours at the beginning of the test period, and for 30 min at the very end 80A GeV beams were delivered to NA61 only for several hours At the beginning of the test period, tests were not possible The tested 13.9 A GeV/c secondary beams (about 36 hours) are the most difficult (lowest yields and beam line stability …) among beams needed by NA61. Results presented below mainly concern the 13.9A GeV/c beams

Ion identification: charge B Be Li He

Ion identification: mass Li He Be B C O

T2 target: 18 cm Be Degrader: none Beam line: A/Z = 11/6, with energy loss correction COLL12: -10 / +20 mm He Li Be B C N O

T2 target: 18 cm Be Degrader: 4 cm Cu Beam line: A/Z = 11/6, with energy loss correction COLL12: +/- 10 mm He Li Be B C N O

T2 target: 18 cm Be Degrader: 4 cm Cu Beam line: A/Z = 11/6, with energy loss correction COLL12: -5 / -3 mm He Li Be B C N O

T2 target: 18 cm Be Degrader: 4 cm Cu Beam line: A/Z = 11/6, with energy loss correction COLL12: +8 / +12 mm He Li Be B C N O

Isotope composition Be Only single isotope (7) is seen C Two isotopes (12,11) seem to be present, possibly due to use of the long Be target

T2 target: 18 cm Be Degrader: 1 cm Cu Beam line: A/Z = 11/6, with energy loss correction COLL12: -20 / -15 mm He Li Be B C N O 20%

Beam intensity study T2 target: 18 cm Be Degrader: 1 cm Cu Beam line: A/Z = 11/6, with energy loss correction COLL12: -20 / -15 mm Carbon fraction of about 20% and can be still significantly increased by optimization of the COLL12 position/opening Carbon yield scaled to 106 particles on S1 gives 4000 C per spill The measured Carbon flux is about ten times lower than the expected one. Clearly an significant improvement can be reached by: -further optimized beam profile on the T2 target (more all-ions), -optimized beam line. -at higher energies the flux is expected (simulation) to be much higher

30 min of the beam at 80A GeV/c on December 6, 2010 Pb

30 min of the beam at 80A GeV/c on December 6, 2010 no degrader degrader

Conclusions Secondary ion beams were produced in the H2 beam line at 13A and 80A GeV/c The results of the test suggest that it is possible to reach physics requirements of NA61 The following improvements are needed before the 2011 physics run: -preparation of the SPS cycles which allow to run NA61 during the LHC fillings, -improve spill structure (make it as much as possible flat), -decrease time density of particles in spill (spills longer or less injections per spill) -more efficient use of the primary beam at the T2 target (better focus, thicker target), -dedicated instrumentation of H2 and NA61 for a fast tunning of secondary ion beams (charge measurement at high particle rates), -allow for more precise setting of the magnet currents, -allow users to check status of all relevant beam line elements (target, degrader, wobbling angle, ...) via CESAR,

Many thanks to all of you!!! (wine and cheese end-of-run meeting: today at 17:00 in 892-1-B09) Pb