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

2. 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 it is significantly (several years)
delayed due to a schedule conflict with the LHC
Thus, the secondary ion beams are very crucial
for a timely execution of the NA61 program

3. 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/c
-primary beams: Ar and Xe at 10A, 20A, 30A, 40A, 80A, 158A GeV/c

4. Progress and plans in data taking for CP&OD
Pb+Pb
NA49 ( )
Au+Au
STAR ( )
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
energy (A GeV/c) T
-test of secondary ion beams

5. 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

6. Search for the onset of the horn in collisions of light nuclei
Study the onset of deconfinement ?
energy (A GeV/c)
Search for the onset of the horn
in collisions of light nuclei

7. T µB Search for the critical point energy A 13 Critical Point:
freeze-out close to critical point,
and system large enough,
expected signal: a hill in fluctuations T
energy
Pb+Pb A 13 µB

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

9. Secondary in beams: the 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
Secondary in beams: the fragment separator
Be 18 cm
Cu 4 cm
500 m

10. Secondary in beams: the NA61 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)

11. 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

12. 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

13. Beam intensity in spill is strongly time dependent
13A GeV/c
80A GeV/c

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

15. 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%) fraction of all triggered events are accompanied
by other beam particles within a several micro-seconds window.
Flatter and longer spills are needed
(a single/double injection cycle should significantly help)

16. Optimization of the 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
This would lead to an increase of particle intensity by a factor of about 3

17. 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 15 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 13.9A 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

18. Ion identification: chargeB Be Li He

19. Ion identification: massLi He Be B C O

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

21. T2 target: 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

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

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

24. Isotope composition Be Only single isotope (7) is seen C
Two isotopes (12, 11) seem to
be present, it is possibly due to
use of the 18 cm long Be target

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

26. Beam intensity study T2 target: 18 cm Be Degrader: 1 cm Cu
Beam line: A/Z = 11/6, with energy loss correction
COLL12: / -15 mm
Carbon fraction of about 20% and can be still significantly increased by
optimization of the COLL12 position/opening
Carbon yield scaled to 3x106 particles on S1 gives C per spill
(this assumes all beam Pb particles to interact on the T2 target)
The measured Carbon flux is about four times lower than the expected one.
Clearly an significant improvement can be reached by
an optimization of the fragment separator parameters beam line.
Furthermore the carbon flux is expected (simulation) to be much higher
than at the lowest one, 13.9A GeV/c.

27. 15 min of the beam at 80A GeV/c
on December 6, 2010 Pb

28. 15 min of the beam at 80A GeV/c
on December 6, 2010
no degrader
degrader

29. NA61 wish list
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 tuning of secondary
ion beams (charge measurements at high particle rates),
-allow for a more precise setting of the magnet currents,
-simplify/improve a procedure of loading a required beam line configuration,
-allow users to check status of all relevant beam line elements (target, degrader,
wobbling angle, ...) via CESAR,

30. Summary
The H2 beam line at the CERN SPS was converted into a fragment
separator and its functionality was successfully tested
The primary Pb beam at 13.9A GeV/c, the lowest ever energy per nucleon
in SPS, was accelerated and extracted to the H2 beam line
The production of secondary beams of light nuclei (A < 16) was studied
at 13.9A and 80A GeV/c
The test allowed to identify numerous modifications needed to improve
production performance of secondary ion beams
The results indicate that it is possible to reach physics goals of NA61
by use of secondary light ion beams produced by the H2 fragment
separator

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