Experimental Storage Ring - ESR E max = 420 MeV/u, 10 Tm, electron-, stochastic- and laser cooling. Indian Institute of Technology Ropar

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1 Experimental Storage Ring - ESR E max = 420 MeV/u, 10 Tm, electron-, stochastic- and laser cooling

2 Specification of the ESR Particle detectors Re-injection to SIS Two 5 kv rf-cavities Fast Injection Schottky pick-ups Gas jet e - cooler I = ma L = 108 m =1/2 L SIS p = mbar E = MeV/u f MHz β = Q h,v 2.65 Six 60 0 dipoles Bρ 10 T m Extraction

3 What is beam cooling? Cooling is synonymous for a reduction of beam temperature Temperature is equivalent to terms as phase space volume, emittance and momentum spread Beam cooling processes are not following Liouville s Theorem: (which neglects interactions between beam particles) In a system where the particle motion is controlled by external conservative forces the phase density is conserved Beam cooling techniques are non-liouvillean processes e.g. interaction of beam particles with other particles (electrons, photons) Benefit of beam cooling: Improved beam quality (precision experiments, luminosity increase)

4 Beam cooling at the ESR What is cooling? What is temperature? 3 k T 2 = 1 = m 2 v 2 = v is the velocity relative to a reference particle, which moves with an average ion-velocity. The temperature is a measure of the random movement. In an accelerator T = 2 2 = M c β p / p 2 T = M c β γ ε 1 β H + 1 β V Why beam cooling? Improve of the beam quality smaller beam size and reduction of the emittance broadening of the energy better beam intensity, accumulation lifetime of the beam Kühlmethoden Stochastische Kühlung Laserkühlung Makroskopische Elektronkühlung Emittanz

5 Beam temperature Thermal particle motion (temperature is conserved) at rest (source) low energy high energy temperature llllllllllllllllllllllll tttttttttttttttttttt 1 2 kk BBTT = 1 2 mmvv 2 = 1 2 mmcc2 ββ 2 δδpp pp 1 2 kk BBTT = 1 2 mmvv 2 = 1 2 mmcc2 ββ 2 γγ 2 θθ 2 2

6 Electron cooling electron collector electron gun I: ma v e = v ion high voltage platform E e = m e /M ion E ion magnetic field electron beam ion beam in beam frame: cold electrons interacting with hot ions e.g.: 200 kev electrons cool 400 MeV/u ions electron temperature: kk BB TT 0.1 eeee kk BB TT mmmmmm superposition of a cold intense electron beam with the same velocity momentum transfer by Coulomb collisions cooling force results from energy loss in the co-moving gas of free electrons G.I. Budker, At. En. 22 (1967) 346 G.I. Budker, A.N. Skrinsky et al., IEEE NS-22 (1975) 2093

7 Electron cooling momentum spread Δp/p = 10-5 diameter 2 mm The ions get the sharp velocity of electrons, small size and divergence G.I. Budker, At. En. 22 (1967) 346 G.I. Budker, A.N. Skrinsky et al., IEEE NS-22 (1975) 2093

8 Stochastic cooling: Implementation at the ESR long. Kicker transv. Pick-up Combiner- Station transv. Kicker long. Pick-up ESR storage ring Stochastic cooling is in particular efficient for hot ion beams

Principle of stochastic cooling Self correction of ion trajectory Using a pick-up probe, the position of the ion beam is measured at a fixed position via the induced signal.

9 Principle of stochastic cooling Self correction of ion trajectory Using a pick-up probe, the position of the ion beam is measured at a fixed position via the induced signal. A deviation of the beam from the ideal orbit can be corrected by amplification of this signal. The amplified signal is now used as a correction signal which acts on the beam at a second position (zero crossing of the betatron function) via a "kicker. The Nobel Prize in Physics 1984 Simon van der Meer 1925*, CERN This method was invented for the cooling of hot p(bar) by van der Meer. He showed that after a cooling time of τ N/C (N: particle number, C = Bandwidth of the amplifier) a momentum width of the beam of about p/p 10-3 can be achieved by stochastic cooling. Detection of the W boson from p p(bar)

10 Principle of laser cooling 1. Absorption of photons from a laser beam: Energy and momentum must be conserved. 2. Absorption of photons: Momentum transfer in a defined direction (directed momentum transfer). 3. No defined direction for the spontaneous emission (isotropic re-emission): Momentum transfer cancels out over many absorption-emission-cycles.

11 Principle of laser cooling 2-step process

12 Cooling D. Boutin

13 Cooling with the ESR

14 Schottky-Mass- Spectroscopy 4 particles with different m/q time

15 Schottky mass spectroscopy Sin(ω 1 ) Sin(ω 2 ) Fast Fourier Transform Sin(ω time 3 ) ω 4 ω 3 ω 2 ω 1 Sin(ω 4 )

16 Small-band Schottky Schottky mass spectroscopy frequency spectra W Pt Bi Hg 78+ Pt Hg Bi Ir Au Os Pt Ir Po Bi Au 77+ W Pt 77+ Ir Hg Bi X q+ Os Lu W Tl Pb 81+ Tm68+ Dy Tb Gd Hf known masses unknown masses Pt Pt Ir 182 Po Os q X Bi Hg Au Er Ho Nd 60+ I Gd63+ A Lu 161 Dy Number of channels 2 Recording time 30 sec Frequency / khz / Frequency Tl 80+ Yb 77+ Ir A Pt Pb 80+ Re W 66+ Ho 80+ Tl Bi Hg 80+ Ir Pr Eu 62+ Sm62+ Pb Bi 82+ Re Dy 65+ Tb Pt 78+ Ir 150m,g Hg Cs 189 Au79+ Os Tm Er Yb Pt 78+ Ta72+ Au Au Pb Pb Tl 197 Hg Os Tm Bi Pb Tl Hf Tl 81+ Po 83+ Au Hg 79+ Tb Ta Hg Tl Lu 200 Au 79+ mass unknown Tl 83+ Re Ir massau knownpo Hg 78+ Po Re Hf 71+ Pt Au Pb Pb Bi 82+ Po Pb Pb 80+ Er Au Po 82+ Bi m,g Tl 79+ Pt Intensity / arb. units Intensity / arb. units Hg Bi Pb Pb 81+ Tl 80+ Bi 82+ Ta 5 Hf Hz

Orbital electron capture decay of stored highly-charged ions

Orbital electron capture decay of stored highly-charged ions EMMI Workshop, 28. June 2010 Nicolas Winckler, MPI-K Heidelberg 1. Experimental setup 2. Many-ion decay spectroscopy 3. Single-ion decay spectroscopy