ACCELERATION AND STORAGE OF ION BEAMS AT CERN
R. Alemany Fernandez BE/OP-SPS OVERVIEW OF THE CERN ACCELERATOR COMPLEX LHC 27 km
SPS 7 km
ION accelerator complex SPS does not operate partially strip ions does not have sublimation pumps and the vacuum is 10-6 – 10-8 mbar in average source of main SPS concern for the GF study LHC
This part of the complex runs STRIPPER FOIL routinely partially strip ions Pb54+ Pb82+ PS This is why LEIR and PS are instrumented with sublimation pumps. Vacuum: 10-10 mbar in LEIR average. SOURCE+LINAC3 PB ION SOURCE
Small sliver of solid isotopically pure 208Pb is placed in a ceramic crucible that sits in an "oven"
The metal is heated to around 800°C and ionized to become plasma. Ions are then extracted from the plasma and accelerated up to 2.5 keV/nucleon Pb29+. The source can also be set up to deliver other species… Ar, Xe, etc LINAC3
Stripping foil Pb29+ Pb54+ Stripping Efficiency is 20% Interdigital-H (IH) linac 4.2 Pb29+ 2.5 keV/nucleon MeV/nucleon
RFQ
LINAC 3 LOW ENERGY ION RING (LEIR)
LEIR accumulates the 200 µs pulses from Linac3; then splits into 2 bunches
Electron Cooling is used to achieve the required brightness
Acceleration to 72 MeV/nucleon before transfer to the PS
LEIR Cycle is 3.6 s LOW ENERGY ION RING (LEIR)
EXTRACTION INJECTION
E-COOLER
80 m circunference PROTON SYNCHROTRON (PS)
PS: The oldest functioning machine at CERN The first Alternating Gradient Machine!
SPS Combined-function magnets (QFQDB) LHC
628 m, Pb54+ @5.9 GeV/u 1970-1976 1959 LHC Cycle time = 3.6 s PS First evidence of weak neutral currents (Zo) LEIR SOURCE+LINAC3 GARGAMELLE SUPER PROTON SYNCHROTRON (SPS) North area
LHC~ 7 km, Pb82+ @177 GeV/u, 1976 SPS AWAKE
HiRadMat 2 T conventional SppS- - has probed the inner structure of protons separated-function - investigated matter antimatter magnets asymmetry 1983 - searched for exotic forms of W,Z matter
RF SEPTUM LARGE HADRON COLLIDER (LHC)
27 km, Pb82+ @2.8 TeV/u, 2008
Betatron cleaning collimators
IP8 IR7 IP1 IR6 SPS (~7 km) LARGEIP5 HADRONLHC COLLIDER (27 km) (LHC) IP2
Sector 34 Momentum cleaning collimators RF IR4 ARC IR3 EXCEPCIONALLY PSI IN SPS IN 2003 FOR ENERGY CALIBRATION
lifetime of Pb53+ in the SPS was 5.3 s at
pPb/Q of 26 GeV/c, limited by the vacuum conditions. PERFORMANCE OF SPS LEAD ION BEAMS IN 2018
Great versatility of the PS RF system, allows different filling patterns:
First half of the 2018 run with 4 bunch (100 ns) scheme
Second half of the 2018 run with 3 bunch (75 ns) scheme
Cycle with up to 14 injections, demonstrated expected performance PERFORMANCE EVOLUTION OVER THE LAST YEARS
Only slip stacking can close the gap SPS SLIP STACKING FOR IONS
• From 100 ns bunch spacing 50 ns bunch spacing more bunches into LHC more luminosity • New SPS LLRF installed during LS2 will allow to perform this operation. Beam commissioning time in 2021 is needed. LEAD IONS PARAMETER TABLE ACROSS COMPLEX XeXe collisions in LHC PSI IN SPS AND LHC IN 2017-2018 Why Xe in 2017?
1. No LHC heavy ion collisions in 2017. Only NA61 fixed target experiment that requested Xe54+
2. Careful setup needed (long ~2 s energy plateau + RF setup for transition crossing) several days needed only for first injection, RF set up and tune, orbit & chromaticity corrections
3. No additional hardware required
4. Xe39+ injected into SPS by removing the TT2 stripper Many test days no standard operation 23.6 Q GeV/C 270 Q GeV/C needs expert
support: Intensity (1e8) Intensity equivalent(1e8) p+ 1.14-15.09.2017 2.13-19.10.2017 3.08.11.2017 4.22.11.2017
time (ms) LEASONS LEARNT
1.First time Xe39+ in SPS non-standard operation needs a lot of time 2.Many measurements performed which allowed a detailed study of the life time 3.Optimization of the stripping schema using existing resources 2. Used as preparation of the machine development studies in SPS and LHC in 2018: • Getting more operational experience with PSI • Preparing the software tools for the data analysis ION STRIPPING SCHEME FOR THE 2018 MACHINE STUDIES – THE “MINIMAL INTERFERENCE” APPROACH
GF _Aluminium stripper
Pb+81
Pb+54 26.01.2018 The 150mm ( 212mm crossed by the beam as installed at 45 degrees) thick Al foil has been installed on the FT16.BTV352 in the TT2 line!. +81,+80
+81,+80 H dispersion = -4 TT10.BTV.100359 m +80,+81,+82 H dispersion ~ 0 m
Pb+54
+80,+81,+82 Stripper: 150mm ( 45o inclined 212mm crossed by the beam) thick Al foil Pb+54
TT10.BTV.100123
BE/BI: S. Burger et al. TT2.BTV.352 JUNE 2018 MDS - FIRST RESULTS
Pb80+ GF _Aluminium stripper +80,+81,+82
Preliminary BCT measurements suggest: • 30% stripping efficiency for 80+ • 50% stripping efficiency for 81+ 24 No systematics analysis yet +80,+81,+82
+80,+81,+82 TT10.BTV.100359
Pb+54
27 June 2018 Stripper: 150mm ( 45o inclined 212mm crossed by the beam) thick Al foil Pb+54 25 TFS.BTV.379 BE/BI: S. Burger et al. (proton equivalent) Pb81+ bunch intensity, two bunches from PS
H&V Emittance ~ 1um rad
Pb81+ IN SPS Close orbit at injection for Pb81+ Pb81+
Injection Ramp Flat top 17.28 GeV/c 270 GeV/c proton equivalent proton equivalent
Life time at flat top for Pb81+ ~ 600 s Life time at flat top for Pb80+ ~ 200 s
Bunch intensity at flat top for Pb81+ = 8e9 elementary charges (enough to be sent to LHC) !! Pb80+ Pb81+
28 Pb80+Pb81+
Champagne!!!!
29 PB81+ TO LHC
• 12 hours LHC machine studies time on 25.07.2018
• Inject new particle “species” in the LHC Pb81+
• Establish a few circulating bunches. Acceleration and storage of partially stripped ions Study of beam lifetime and beam parameter evolution at injection and top energy Beam loss characterization CONCLUSION
• AN IMPORTANT MILESTONE OF THE GAMMA FACTORY STUDY WAS ACHIEVED IN 2018 INJECTION, ACCELERATION AND STORAGE OR THE Pb81+
• To get there, an important amount of time and resources where needed because THIS IS NOT YET STANDARD OPERATION AT SPS • The success of those tests open the road for the next crutial milestone at CERN the SPS proof of principle experiment