Isochronous Mode of the CR Sergey Litvinov Novosibirsk, 17 November 2015

Introduction National Research Council's board on physics and astronomy 02.01.2002 The 11 Greatest Unanswered Questions of Physics “Resolution of these profound questions could unlock the secrets of existence and deliver a new age of science within several decades” 3. How were the heavy elements from iron to uranium made? ---- Remove test by Eric Haseltine, llustrations by Dan Winters & Gary Tanhauser

Stellar nucleosynthesis: fusion until iron ---- Remove test 3

s-only rp-process rp-only r-process r-only neutron number s process: slow n-capture and β- decay near valley of β stability (from Rene Reifarth) s-only rp-process neutron number proton number Zr 80Br, t1/2=17 min, 92% (b-), 8% (b+) Y Sr (n,g) Rb rp-only Kr Br 85Kr, t1/2=11 y (b-) Se As r-process 79Se, t1/2=65 ky (b+) Ge Ga Zn r-only Cu Ni 64Cu, t1/2=12 h, 40% (b-), 60% (b+) Co 63Ni, t1/2=100 y Fe

The r (rapid neutron capture) - process: termination point: fission of very heavy nuclei waiting points Rolfs & Rodney: Cauldrons in the Cosmos, 1988 ---- Remove test typical lifetimes for unstable nuclei far from the valley of b stability: 10-4 – 10-2 s Requiring n capture time: tn ~ 10-4 s  Nn ~ 1020 n/cm3 explosive scenarios needed to account for such high neutron fluxes The r–process creates about 50% of nuclei; its site is still unknown 5

Are Supernovae IIa the sites of the r-process? A possible scenario: Supernovae IIa provide in the second of their outbreak a huge neutron flux creating a plenty of unstable neutron-rich nuclei that decay by a chain of beta decays towards the valley of stability ---- Remove test 6

Why do we need the Isochronous Mode? To determine the r-process we have to measure masses of neutron-rich exotic nuclei with a high accuracy of (Δm/m~10-6). 1. Revolution frequency difference (or revolution time) of two particles with different m/q ratio circulating in the ring can be written as: 2. Transition energy gt is: 3. Isochronous condition: g = gt Thus, all nuclei with the same m/q at different velocities travel around the ring with equal revolution times. ---- Remove test Isochronous Mass Spectrometry (IMS) is one and only quick and sensitive enough technique for mass measurements of large number of extremely short exotic nuclei. H. Wollnik et al., “Experiment Proposal for the SIS-FRS-ESR Facilities”, (1986). 8

Collector Ring (CR) ---- Remove test 9

Different CR Isochronous Settings ---- Remove test r-process can be reached at Bρ~9-10 Tm, the dipole B-Field has to be stable for different magnetic rigidity. 10

Isochronicity curve +Magnets errors 10xZoom Zoom 10xZoom Super-FRS + CR CR is coupled to the Super-FRS facility and will among other tasks operate as an isochronous storage ring. As I mentioned before my task was to investigate and design the isochronous mode of the CR Zoom 11

One has to cut tails (reduce momentum acceptance)! Bρ Tagging Experimental isochronicity curves in the ESR Good isochronous conditions are fulfilled only in a small range. One has to cut tails (reduce momentum acceptance)!

Solution: measurement of Bρ or v in addition Bρ Tagging Isochronous experiments at the ESR With tagging the resolution is improved but transmission of exotic nuclei is worst. Solution: measurement of Bρ or v in addition H. Geissel et al., Hyper. Inter. 173 (2006).

2 TOF detectors εx= εy=100 mm mrad from Super-FRS x/y (TOF2) = 59/42 mm ΔL=18m TOF detectors are not symmetric regarding to the middle quarupole TOF signals depend from the detectors‘ position. x/y (TOF1) = 56/42 mm

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Influence of octupole imperfections To investigate the influence of high-order harmonics, the strength of octupoles was changed by 1, 2, 5 and 10% from the calculated ones. The corresponding Monte-Carlo simulations have been performed and TOF signals at the CR symmetry point have been plotted. For the deviation of 1% the TOF signal width is almost not changed. For 2% deviation the signal is already wider by factor 1.5 So, the octupole field error should not exceed 1%.