A new storage ring for ISOLDE

Transcription

1 A new storage ring for ISOLDE Manfred Grieser Max Planck Institut für Kernphysik, Heidelberg ISOLDE facility at CERN NARRS workshop, GSI, Darmstadt, 13 th -15 th March

2 Proposed project to store radioactive ions for nuclear physics experiments it was proposed to move TSR located at MPI for nuclear physics to ISOLDE. TSR storage ring in operation until December

3 HIE-ISOLDE HIE-ISOLDE tilted beam-line coming from the HIE-ISOLDE machine. possible TSR installation above the CERN cable-tunnel. (E. Siesling) TSR@HIE-ISOLDE building 3 3

4 Time-line of the project workshop at MPI-K Heidelberg evaluated the future for TSR Oct 2010 ISOLDE and Neutron Time-of-Flight Committee endorsed Jan 2012 TSR technical design report 129 co-authors (47 institutions) EPJ Special Topics May 2012 Approved by CERN Research board, May 2012 The installation of TSR, as an experiment to be included in the HIE-ISOLDE programme, was approved by the Research Board. The timescale will be defined once the study of its Integration has been completed. Presentation of the integration study to the CERN Research Board Nov 2013 Several workshops at CERN: 2012, 2014, 2015 Updated CERN integration study with report to the CERN directorate 2016 CERN director general: decision about the project is postponed until 2020/2021 (after second LHC upgrade ) August/September 2016 MPIK cannot hold TSR at MPIK until 2020/2021 without getting green light from CERN 4

5 Design Criteria of the new storage ring a) storage ring should be able to store ions up to 238 U and 10 MeV/u at the equilibrium charge state obtainable with the HIE-ISOLDE stripper. Þ maximum rigidity of the ring: Br max»1.5 Tm b) storing of heavy daughter nuclei up to a certain rigidity deviation (DBr/Br) created in nuclear reactions should be possible. Þ small maximum dispersion function D x of the storage ring dispersion at the gas jet D x =0 m to avoid a excitation of betatron oscillation of daughter nuclei c.) daughter nuclides with large transfers momenta produced in nuclear reactions should be focused at the detector position d.) storing ring should be compact to fit in the present HIE Isolde hall gas target detector plane quadrupoles dipole magnet

6 Layout of the new storage ring with straight section Length L=3.5 m and circumference C=42.4 m D x =0 m (achromatic mode) 6

7 principle ECOOL Stacking A combination of multi-turn injection and electron cooling stacking will be used to fill the storage ring with particles particle number N(t): dn(t) dt = n r N i N(t) - t N i -injected particle number per injection n r - injection rate t- total lifetime 7

8 Luminosity with ECOOL stacking In the equilibrium: number of stored ions N 0 (N 0 N s ): N N 0 determines the luminosity L: R L= = N f n =n τn N f σ dn (t) / dt = 0 N 0 - equilibrium particle number 0 = nr t Ni 0 0 t r t i 0 τ! 1 n t N s -space charge limit R- reaction rate s- cross section N i -injected number of ions with multi-turn injection n t - target thickness n- target density f 0 -revolution frequency n r -injection rate n r =1/T T- time between two injections for large n t the total life time t given by the target thickness n t : n t = ò nds R L= =const N σ T independent of target thickness! i number of ions per multi turn injection time between two multi turn injections 8

9 Effective Luminosity -continuous injection cycle -measurement starts after the cooling time T cooling of the injected ions and ends before the next multi-turn injection takes place injection and measuring scheme T measurements T cooling T e multi turn injections measurements t Luminosity is reduced by factor h=t e /T Þ effective Luminosity L eff : R τ L = =η N f n =η f n N σ T eff 0 0 t 0 t i N 0 -total number of stored particles N i -injected particle number per multi-turn injection T- time between two injections t- total lifetime f 0 -revolution frequency 9 below space charge limit N 0 N s N s -space charge limit

10 Space charge limit due to incoherent tune maximum possible stored ion number: A 2p 2 3 Ns = B b g e (-DQ) 2 q r -DQ - possible incoherent tune shift for B=1 at TSR: -DQ» æ q Ns 1 ö 2 e µ ç 2 3 A q 2 lcool b lcool µ ne ne µ b è ø A incoherent tune shift for an electron cooled ion beam N s for an electron cooled ion beam: (A /E ) =const 2 q /28 E-ion energy in MeV A-ion mass q-ion charge state p new storage ring (ISR) has similar possible incoherent tune shifts Measured space charge limit of an electron cooled ion beam at the TSR Ion E (MeV) measured N s calculated N s p O C TSR experiments: const» S Cl l Þ maximum possible Luminosity for N 0 =N s 10

11 L beam Effective Luminosity of some selected ions =ηn f n eff 0 0 t Energy (MeV/u) calculated for the space charge limit (N 0 =N s ) and a beam life time t=1-1.5s q s N s target n t t (s) N i /T 2 (atoms/cm ) (1/s) L eff 2 (1/cm s) 86 Kr H Ru H Hg H h=0.5 proton capture reactions 232 Th H 2,D U H 2,D Th He fission reactions 238 U He injection charge state green: bare ion black: equilibrium charge state after HIE-ISOLDE stripper N s -space charge limit of an electron cooled stored ion beam required injection rate (ions/s) for N 0 =N s n t -target thickness calculated for a beam life time: t=1-1.5s remark: H 2, D 2, He target: limitation of n t»10 14 atoms/cm 2 all required injection rate N i /T for the space charge limit N s maybe can not be reached 11

12 Proton capture reaction for the astrophysical p-process 1. Nuclear reactions momentum conservation rigidity daughter ion A+1 Y (q+1)+ A X q+ + p A+1 Y (q+1)+ + g A m v =(A+1) m v Þ Þ 0 p 0 Avp v= (A +1) p A Bρ= = Q (+)e q 1 2. Ionization projectile: A X q+ A X (q+1)+ + e p A rigidity stripped ion A X (q+1)+ Bρ= = mv 0 p Q (q+ 1)e0 Þrigidities of A X (q+1)+ and A+1 Y (q+1)+ are equal Þ A X (q+1)+ and A+1 Y (q+1)+ can not separated with magnetic fields! Þ A X (q+1)+ and A+1 Y (q+1)+ ions are at same detector position 0 mv 0 p A X q+ - stored main ion q- charge state main beam A- mass number A+1 Y (q+1)+ -daughter nuclide p- proton from hydrogen target same rigidity!!!!! Þa) experiment has to carry out with bare A X q+ ions Þb) bare ions for heavy systems A X q+ cannot produce by stripping at 10 MeV/u! looking for solutions to separate A X (q+1)+ from A+1 Y (q+1)+ : accumulate A X (q+1) in the storage ring and separation with electron cooling 12

13 Proton pick up reactions by storing daughter nuclei example: Hg + p Tl g 16 electrons are left! daughter nuclei Tl 65+ should be kept and accumulated in the storage ring Þ storage ring has to operate in an achromatic mode with D x =0 m in the gas target to avoid excitation of betatron oscillations of the daughter nuclei: production of daughter with DBr/Br betatron oscillation gas jet betatron oscillation of primary ion of daughter nuclide x ΔBρ Δx=Dx Bρ s Dx Achromatic mode D x,max smaller compare to TSR closed orbit of primary ion closed orbit of daughter nuclide for Dx¹0 m gas target 13

14 Shift of the ion orbits by electron cooling reaction: Hg + p Tl g 65+ direct after injection: v(tl ) < v 65+ e v(hg ) = v e with electron cooling: change of the rigidity of Tl 65+ : 65+ v(tl ) v e DBρ Bρ 65+ v(hg ) = v e 1 A-q = - - q+1 A(1 + q) v-electron velocity e v(hg ) Hg velocity of v(tl ) - velocity of Tl A- mass of main beam q- charge of main beam measurement of luminosity 14

15 Scraping of electron captured daughter nuclides rate equation to determine N d cooled main beam scraper dn dt d (t) Nd (t) in the equilibrium cross section N σ= Lτ = L s - d,0 d t d number of accumulated daughter nuclei total life time of daughter nuclei example life time should not depend of resonances beam: 196 Hg 64+,E/A=10 MeV/u,N 0»N s /6=3 10 7, n t = atoms/cm 2 Þ» 27 2 L= / cm s, τd 3.5s for: s=0.01 barn : N d,0 =σ Lτd Þ Nd,0» 80 15

16 Direct Detection of the produced daughter nuclei vh vertical kicker detector plane A vertical kicker is used to kick the stored ion beam towards the detectors second experimental straight section II -50 kv ion beams detector After reaching the equilibrium daughter nuclei number given by: Nd,0 = Lτσ d The kicker voltage is switched on very quickly with Behlke switches to deflect the stored ion beam to the detectors located above to the stored ion beam, where the switching time T<<T 0 (T 0 -revolution time) +50 kv stored ion beams 16

17 Multi Charge operation of the TSR - Storing also daughter nuclei after production needs a relative large momentum acceptance of the storage ring - At the TSR it was shown that several beams with different rigidities can be stored at the same time Confirmation of the multi charge operation at the TSR Schottky noise measured 12 s after injection dispersion in the cooler: D x =0.3 m injected ion beam E=266 MeV DBρ = Bρ 0.04 DBρ = Bρ produced by electron capture visible already 2-3 s after injection produced by stripping detectable 8 s after injection 17

18 Possible location of the new storage at HIE-ISOLDE transparency from Erwin Siesling and Stephane Maridor, CERN service tunnel extension of HIE ISOLDE hall HELIOS HIE-ISOLDE 18

19 Acknowledgement Klaus Blaum, MPI für Kernphysik, Heidelberg Jan Borburgh, CERN, Geneva Beatriz Jurado, CENBG, Gradignan Stephane Maridor, CERN, Geneva Akira Noda, NIRS, Chiba Erwin Siesling, CERN, Geneva Fredrik Wenander, CERN, Geneva 19