Manipulation of transverse beam Manipulation of transverse beam - PowerPoint PPT Presentation

Manipulation of transverse beam Manipulation of transverse beam distribution in circular accelerators: distribution in circular accelerators: beam splitting by particles’ ’ trapping trapping beam splitting by particles into resonance islands into resonance islands M. Giovannozzi M. Giovannozzi Summary: Summary:  Introduction Introduction  Other applications Other applications    Present multi Present multi- -turn extraction turn extraction  Measurement results Measurement results    Conclusions Conclusions  New multi New multi- -turn extraction (MTE) turn extraction (MTE)   Massimo Giovannozzi Oxford - - July 4th 2013 July 4th 2013 1 Massimo Giovannozzi Oxford 1

Introduction - - I I Introduction Three approaches are normally used to extract beam Three approaches are normally used to extract beam from a circular machine: from a circular machine: Fast Extraction (one turn) Slow Extraction (millions Fast Extraction (one turn) Slow Extraction (millions turns) turns) A kicker (fast dipole) A kicker (fast dipole) displaces the beam from displaces the beam from The separatix separatix of the third- - The of the third nominal closed orbit. nominal closed orbit. order resonance increases order resonance increases turn! -turn! particles’ ’ amplitude until they particles amplitude until they A septum magnet deflects A septum magnet deflects jump beyond the septum. jump beyond the septum. displaced beam towards displaced beam towards Multi- transfer line. transfer line. The tune is changed tune is changed to shrink to shrink Multi The the stable region, thus pushing the stable region, thus pushing This extraction can be used This extraction can be used the particles towards larger the particles towards larger both to transfer beam both to transfer beam amplitudes. amplitudes. towards a ring or an towards a ring or an experimental area. . experimental area This extraction is used to This extraction is used to transfer beam towards an transfer beam towards an What is in between? What is in between? experimental area. . experimental area Massimo Giovannozzi Oxford - - July 4th 2013 July 4th 2013 2 Massimo Giovannozzi Oxford 2

Introduction - - II II Introduction Multi- -turn extraction turn extraction Multi The beam has to be “manipulated manipulated” ” to increase the The beam has to be “ to increase the effective length beyond the machine circumference. effective length beyond the machine circumference. This extraction mode is used to transfer beam between transfer beam between This extraction mode is used to circular machines. . circular machines AT CERN this mode is used to transfer transfer the proton beam the proton beam AT CERN this mode is used to between PS PS and and SPS SPS. In the SPS the beam is used for . In the SPS the beam is used for between Fixed Target physics (broad sense) Fixed Target physics (broad sense) Neutrino experiments (until 1998) (until 1998) Neutrino experiments CERN Neutrino to Gran Sasso (CNGS) (from 2006) (CNGS) (from 2006) CERN Neutrino to Gran Sasso 13 p These beams are high high- -intensity intensity (about (about 3 3× ×10 10 13 p in the in the These beams are PS). PS). Massimo Giovannozzi Oxford - - July 4th 2013 July 4th 2013 3 Massimo Giovannozzi Oxford 3

Present multi- -turn extraction turn extraction – – I I Present multi C SPS = 11 C PS C SPS = 11 C PS PS PS PS PS SPS circumference SPS circumference First PS batch Second PS batch Second PS batch Gap for kicker Gap for kicker First PS batch Beam current Beam current transformer in the transformer in the PS/SPS transfer line PS/SPS transfer line 1 2 3 4 5 (total spill duration 0.010 ms) 1 2 3 4 5 (total spill duration 0.010 ms) Massimo Giovannozzi Oxford - - July 4th 2013 July 4th 2013 4 Massimo Giovannozzi Oxford 4

Present multi- -turn extraction turn extraction – – II II Present multi Electrostatic Electrostatic Kicker strength Kicker strength septum septum Fifth turn Fifth turn (beam shaving) (beam shaving) Four turns Four turns Slow bump Slow bump Kicker magnets Kicker magnets used to generate used to generate Length Length a closed orbit a closed orbit E field E field =0 =0 bump around bump around X’ X ’ E field ≠ 0 0 E field ≠ electrostatic electrostatic 2 2 septum septum 3 3 5 5 1 1 Slow bump Slow bump X X 4 4 Extraction Extraction Electrostatic septum Electrostatic septum line line blade blade Extraction septum Extraction septum Massimo Giovannozzi Oxford - - July 4th 2013 July 4th 2013 5 Massimo Giovannozzi Oxford 5

Present multi- -turn extraction turn extraction – –III III Present multi The main drawbacks of the present scheme are: The main drawbacks of the present scheme are: Losses (about 15% 15% of total intensity) are unavoidable of total intensity) are unavoidable Losses (about due to the presence of the electrostatic electrostatic septum used septum used due to the presence of the to slice the beam. to slice the beam. The electrostatic electrostatic septum is septum is irradiated irradiated. This poses . This poses The problems for hands problems for hands- -on maintenance on maintenance. . The phase space matching is not optimal (the various The phase space matching is not optimal (the various slices have “ “fancy shapes fancy shapes” ”), thus inducing betatronic ), thus inducing betatronic slices have mismatch in the receiving machine, i.e. emittance mismatch in the receiving machine, i.e. emittance blow- -up up. . blow The slices have different emittances and optical The slices have different emittances and optical parameters. parameters. Massimo Giovannozzi Oxford - - July 4th 2013 July 4th 2013 6 Massimo Giovannozzi Oxford 6

Novel multi- -turn extraction turn extraction – – I I Novel multi The main ingredients of the novel extraction: The main ingredients of the novel extraction: The beam splitting is not performed using a mechanical The beam splitting is not performed using a mechanical device, thus avoiding losses. Indeed, the beam is device, thus avoiding losses. Indeed, the beam is separated in the transverse phase space using separated in the transverse phase space using Nonlinear magnetic elements (sextupoles ad octupoles) to Nonlinear magnetic elements (sextupoles ad octupoles) to create stable islands stable islands. . create Slow (adiabatic adiabatic) tune ) tune- -variation to cross an appropriate variation to cross an appropriate Slow ( resonance. resonance. This approach has the following beneficial effects: This approach has the following beneficial effects: Losses are reduced (virtually to zero). (virtually to zero). Losses are reduced The phase space matching is improved phase space matching is improved with respect to the with respect to the The present situation. present situation. The beamlets have the same emittance and optical The beamlets have the same emittance and optical parameters. . parameters Massimo Giovannozzi Oxford - - July 4th 2013 July 4th 2013 7 Massimo Giovannozzi Oxford 7

Model used in numerical simulations Model used in numerical simulations Standard approach: nonlinear elements Standard approach: nonlinear elements represented as a single kick at the same represented as a single kick at the same location in the ring (H Hé énon non- -like like polynomial location in the ring ( polynomial maps). ). maps Vertical motion neglected. Vertical motion neglected. Normalised (adimensional co- -ordinates). ordinates). Normalised (adimensional co The linear tune is The linear tune is time- -dependent dependent time ˆ ˆ     2 K X X       3     R      ˆ ˆ ˆ ˆ 2    K 2 3 3     X X X X ' '  2 x n 1 n Quadrupoles Sextupole Sextupole Octupole Quadrupoles Octupole Massimo Giovannozzi Oxford - - July 4th 2013 July 4th 2013 8 Massimo Giovannozzi Oxford 8

Novel multi- -turn extraction turn extraction – – II II Novel multi Left: initial phase Left: initial phase space topology. No space topology. No islands. islands. Right: intermediate Right: intermediate phase space topology. phase space topology. Islands are created Islands are created near the centre. near the centre. Bottom: final phase Bottom: final phase space topology. space topology. Islands are separated Islands are separated to allow extraction. to allow extraction. Massimo Giovannozzi Oxford - - July 4th 2013 July 4th 2013 9 Massimo Giovannozzi Oxford 9

Novel multi- -turn extraction turn extraction - - III III Novel multi Simulation Simulation parameters: parameters: Hé énon non- -like like H Tune variation Tune variation map (i.e. 2D map (i.e. 2D polynomial – polynomial – degree 3 - degree 3 - mapping) mapping) representing representing a FODO cell a FODO cell with with Phase space Phase space portrait portrait sextupole and sextupole and octupole octupole Massimo Giovannozzi Oxford - - July 4th 2013 July 4th 2013 10 Massimo Giovannozzi Oxford 10