P2I Alessandro Variola LAL Orsay

P2I Alessandro Variola LAL Orsay
5/23/2018 Alessandro Variola, LAL ORSAY

Alessandro Variola, LAL ORSAY
- Source de positron polarisé et non polarisé pour les futurs collisionneurs - Upgrade des Lignes de mesure RF et du Faisceau dans l'infrastructure PHIL 5/23/2018 Alessandro Variola, LAL ORSAY

Cher Collègue, Suite à la sélection de votre proposition pour l'attribution d'un contrat post doctoral sur le sujet « Source de positron polarisé et non polarisé pour les futurs collisionneurs linéaires» par P2I, nous avons le plaisir de vous annoncer que votre dossier a été retenu par le Conseil de groupement pour un financement en 2009. Vous pouvez donc dès à présent lancer un appel d'offre pour ce contrat post doctoral de la manière la plus appropriée pour votre sujet de façon à pouvoir toucher les meilleurs candidats à des post docs commençant au début de l'année universitaire (le financement étant normalement prévu pour débuter à cette date). Un financement de 94K sur 2 ans vous sera transféré quelques semaines avant le début du contrat. Suite à la sélection de votre proposition pour l'attribution d'une bourse R&D sur le sujet "Upgrade des Lignes de mesure RF et du Faisceau dans l'infrastructure PHIL" par P2I, nous avons le plaisir de vous annoncer que votre dossier a été retenu par le Conseil de groupement P2I pour un financement à hauteur de 30K pour l'instant sur 2 ans. . 5/23/2018 Alessandro Variola, LAL ORSAY

Sources de Positrons CLIC-ILC, Hybrid Source SuperB, HOM capture Both solutions are ‘Baseline’ 5/23/2018 Alessandro Variola, LAL ORSAY

POSITRON SOURCES USING CHANNELING FOR ILC & CLIC
INTRODUCTION * Necessity to consider conventional-like sources * Good results and perspectives for crystal sources using electron channeling in axially oriented * Studies on energy deposition in crystal and amorphous targets confirm the interest of crystals for the total energy deposited which is less than in an amorphous targets giving the same yield. * Simulations and experiments showed that an hybrid scheme (crystal radiator + amorphous converter) is advantageous. Such a solution allows a limited energy deposition in the crystal. 5/23/2018 Alessandro Variola, LAL ORSAY

THE PROBLEM OF PEDD The local and almost instantaneous energy deposition in a target (for instance during a pulse duration) may be very critical for the target survival. Indeed, due to inhomogeneous energy deposition in the target, thermal gradients causing mechanical stresses lead to target destruction as by shock waves. After the SLC target destruction, analyses showed that a maximum value of 35 J/g (in tungsten) must not be exceeded. The PEDD is strongly depending on the incident beam intensity and energy and on its transverse dimensions; it depends also on the thickness of the target. 5/23/2018 Alessandro Variola, LAL ORSAY

THE BASIC SCHEME FOR ILC & CLIC “x” meters e+ g e- e+, e-, g e- Crystal Amorphous Radiator Converter Only the photons are impinging on the converter: that limits the energy deposition in the amorphous target. The yield is less than if the particles coming from the crystal were also impinging on the amorphous target 5/23/2018 Alessandro Variola, LAL ORSAY

* THE CRYSTAL : Photons generated by electrons in channeling conditions and above barrier. * The crystal, axially oriented, may be W, Si, Ge, C(d)… In our case, we choose W in <111> orientation * THE AMORPHOUS CONVERTER: it is made of W * THE DISTANCE RADIATOR-CONVERTER: it is of some meters; here it is 2 meters. It allows the use of sweeping magnet in between. Another possibility is to select also charged particles coming from the radiator (e+, e-) with energy larger than Etreshold to increase the yield e+/e- * IMPINGING ENERGIES: E- = 3, 4, 5 and 10 GeV SIMULATIONS Incident beam: electron beam energy between 3 and 10 GeV and transverse rms radius of 1 and 2.5 mm have been considered Targets: (a) Crystals of 1, 2 and 4 mm thick: for E-=10GeV Amorphous target of 8 mm (b) Crystals of 1.4, 2.4 et 4.4 mm thick for E- =3, 4 and 5 GeV Amorphous target of 10 mm thick Capture system: an Adiabatic Matching Device with a magnetic field decreasing from 6 Teslas to 0.5 Teslas on 50 cms. Iris aperture is ~20mm radius. Accelerating field is 18 MeV/m peak value [SW] Outputs: Simulations have been carried out corresponding to the general scheme. The yield e+/e-, the transverse emittance as the longitudinal emittance have been determined at the end of the solenoid (270 MeV). The capture efficiency has also been determined. 5/23/2018 Alessandro Variola, LAL ORSAY

TABLE OF SIMULATION RESULTS FOR DIFFERENT ELECTRON ENERGIES 5/23/2018 Alessandro Variola, LAL ORSAY

Hybrid Amorphous, CLIC-ILC
INCIDENT BEAM: an incident electron beam of 10 GeV TARGETS: CRYSTAL: a 1 mm thick W crystal <111> orientation AMORPHOUS: a 8 mm thick amorphous target CAPTURE SYSTEM: AMD with decreasing field from 6 to 0.5 Tesla on 50 cms Accelerating field is 18 MeV/m, peak [SW] RESULTS: accepted yield: 1.8 e+/e- (s -=1mm) 1.5 e+/e- (s -= 2.5 mm) PEDD: assuming an incident e- bunch of e- crystal amorphous PEDD/e PEDD/bunch PEDD/e PEDD/bunch s - =1mm 2 GeV/cm J/g/bunch GeV/cm J/g/bunch s - =2.5mm GeV/cm J/g/bunch GeV/cm J/g/bunch It is quite clear that the hybrid target cannot sustain the 2820 bunches and that distributed targets system must be considered. For Clic (less bunches…312) it is feasible . 5/23/2018 Alessandro Variola, LAL ORSAY

LONGITUDINAL EMITTANCE AT END OF CLIC PREACCELERATOR [s -=1mm] Blue: 80% Red: rms ez =9.5pcmMeV For s -=2.5 mm, the emittance shape is very similar and the rms area almost the same 5/23/2018 Alessandro Variola, LAL ORSAY

PROPOSED POSITRON TARGET FOR CLIC 2 m e+ e- g e+, e-, g (5 GeV) e- Crystal Amorphous W: 1.4 mm thick W: 10 mm thick With an incident beam of e-/pulse, we expect e+/pulse at 270 MeV (pulse of 156 ns) Or e+/bunch 5/23/2018 Alessandro Variola, LAL ORSAY

Primary Electron Beam Linac
g/e+ Target e-/g Target Thermionic e- gun Primary electron beam Linac Bunching system 5 GeV Crystal Amorphous Parameter for 3 TeV Unit CLIC Primary e- Beam Energy GeV 5 N e- /bunch 109 7.5 N bunches / pulse - 312 N e- / pulse 1012 2.34 Pulse length ns 156 Repetition frequency Hz 50 Beam power kW 94 Beam radius (rms) mm 2.5 Bunch length (rms) 0.3 Electron beam parameters on the crystal target October 2009 With an yield of 1 e+/e- (at 200 MeV) , the charge is 7.5 x109 e-/bunch on the target. Parameters used for BINP/CERN/IPNL/LAL simulations

PEDD study for CLIC targets
GEANT 4 simulations Distance crystal - amorphous target Power deposited in amorphous target Thickness amorphous target e+/e- CLIC Note 808 Today choice

PROPOSED SCHEME FOR ILC: ONLY IF MULTITARGET A thesis is ongoing!!! 2 meters e+ g e- e+, e-, g e- Crystal multitarget Amorphous multitarget With incident beam of e-/bunch the expected accepted e+ yield is of e+/bunch at 270 MeV (s -=1mm). It is of e+/bunch for s -=2.5 mm 5/23/2018 Alessandro Variola, LAL ORSAY

SUMMARY AND DISCUSSION * Hybrid schemes using a crystal as a radiator and an amorphous target where only g coming from the crystal are sent, have been studied for CLIC and ILC as “conventional” solutions. The simulation results showed accepted yields in accordance with the requirements. The emittances at the end of the preaccelerator (270 MeV) can be improved through optimization of the capture section and bunch compression in the longitudinal phase space; energy compression can also been considered in view of efficient stacking in the damping ring. * One of the main concerns for positron targets is the energy deposited. As demonstrated in recent papers, the total energy deposited is less for a purely cristalline target than for the equivalent (giving the same yield) amorphous target. The Peak Energy Deposition Density (PEDD) is comparable. But using hybrid targets with a separation between the crystal and amorphous parts giving the possibillity of sweeping off part or all the charged particles, allows lowering of the PEDD and henceforth, avoiding multi-target use. That solution can be worked out with CLIC. Concerning ILC, the very intense pulse (> 1013e-) precludes use of a unique hybrid target: both crystal and amorphous systems are multitargets; that makes the crystal solution hard to work out. 5/23/2018 Alessandro Variola, LAL ORSAY

CLIC notes Dynamics on the positron capture and accelerating sections of CLIC The CLIC positron capture and accelertation in the injector LINAC Study of an hybrid positron source using channeling for CLIC 4 Conference proceeding between CLIC and SuperB 5/23/2018 Alessandro Variola, LAL ORSAY

Preger – Guiducci Scheme “new” scheme THERMIONIC GUN SHB 0.6 GeV PC 0.7 GeV BUNCH COMPRESSOR 5.7 GeV e+ 4.0 GeV e- POLARIZED SLAC GUN B graded S band Sections 50 MeV e+ e- combiner DC dipole 0.2 GeV 300 MeV CAPTURE SECTION Diag lina Polarization, en spread Emittance bunch length 0.6 GeV (safety) Diag line Energy, spread, beam size current monitor Separator e+-e- Bunch length Emittance 250 MeV matching Moller polarimeter 4 GeV (straight line) HE diag Emittance,,En spread Monitor Size and position En spread Proposal for Vacuum regions We propose to stay with the SLAC gun in the positron line and to have a custom Polarised, low charge electron sources in the electron line 5/23/2018 Alessandro Variola, LAL ORSAY

Positrons (thanks to Freddy)
- 1) Target production and optimization 2) AMD vs QWT, Parmela, Geant4 and Astra ok 3) Polarization studies (Geant4) – not needed 4) Capture in 4 different scenarios : S band acceleration + S band S band deceleration + S band L band deceleration + L band L band TM020 deceleration + L band 5) Transport (FODO design) up to 1 GeV in the 4 cases 6) Coupling studies 7) GHz cavity design 8) TM020 cavity design : 4 cells will be prototyped in Aluminium 9) Comparison with Dafne source (~ok). Experiment soon? 5/23/2018 Alessandro Variola, LAL ORSAY

Realisations: Design Study of Travelling wave Section (1)
Design of RF structure (using Superfish) Structure with 6 cylindrical cavities Using TM020-2/3 Operating at 3 GHz Design Parameters: Cell dimensions: Rcell ~ 9 cm Lcell ~ 3.331cm Irises dimensions: Riris=1.5 cm Liris= 0.8 cm E-field TM020-2/3 Ez along z-axis 5/23/2018 Alessandro Variola, LAL ORSAY P.Lepercq

Stress and thermal effects
PEDD @200 MeV Pedd J/g/e- @ 300 MeV Pedd J/g/e- @ 500MeV Pedd J/g/e- 6.6e10*5 = e- (10nc 5 bunch) So (max limit 35 J/g) 200 MeV on a PEDD= 0.55J/g 300 MeV on 0.85 J/g 500MeV 1 J/g AVERAGE deposited energy: @200 MeV 52.5 MeV/e- 300 MeV MeV/e- 500MeV 120 MeV/e- Tungsten density g/cm3 So for the different cases in a cubic cm target we have to multiply for 25 (Hz) and ~20 (density) So in the worst case (500 MeV) we have 160W (70 and Not so hard to cool 5/23/2018 Alessandro Variola, LAL ORSAY O.Dadoun

The ACS Accelerating / Deceleration depending on the type of RF cavities within the ACS 1st scenario = GHz full acceleration 2nd scenario = GHz deceleration + acceleration 3rd scenario = GHz deceleration + acceleration 4rd scenario = combination of RF types (using 3 GHz TM020 mode for deceleration and GHz TM010 for downstream acceleration). 5/23/2018 Alessandro Variola, LAL ORSAY

Recap 4 Scenarios under investigation 25MV/m for acceleration Scenario 1 2 3 4 RF (MHz) – strategy acc 2856 – dec (S-band) 1428 – dec (L-band) 3000 dec acc Mean Energy (MeV) 302 287 295 333 Erms (MeV) 21.4 32.3 (12) 16.83 (9.09) 5.2 (3.2) Zrms (mm) 2.7 6.4 8.89 3.5 Xrms (mm) 3.8 4.4 8.0 8.1 X’rms (mrad) 1.02 1.11 1.69 1.4 Ex =X’X (mm.mrad) 4.6 13.0 11.4 Total Yield (%) 2.8 7.53 32.3 31.9 Yield ±10MeV (%) 1.3 3.9 19.6 29.3 With a positron injection of 10 nC and a yield of 3.9%, we will have positrons at 300 MeV ±10MeV (scenario 2 – 2.8 GHz) 5/23/2018 Alessandro Variola, LAL ORSAY

End of 1st Tank – 3000 MHz Scenario 4 Length of 1st tank = ~2.93 m Cell length= 3.331cm Tank Phase f1= 280o Tank Gradient G1=10MV/m Gaussian Fit sz = m Energy (MeV) Energy (MeV) 5/23/2018 Alessandro Variola, LAL ORSAY Z (m) Z (m)

Layout Example Up to ~1050 MeV Acc. Cavity GHz, Peak gradient= 13MV/m 3 GHz 10 MV/m Fodo cells 38  ~160 m Solenoid 0.5 T 0.534.1 m Matching section 34.3 ~38 m 5/23/2018 Alessandro Variola, LAL ORSAY

At end of the fodo accelerating section
3.0 GHz tank (deceleration), ~1050 MeV At ~160 m, after the target. At exit of last cavity, Particles within a cut radius: Energy (MeV) Yield (e+/e-) Total yield Yield ± 10 MeV 1050 ±10 MeV Radius (m) Z (m) 240 pC 5/23/2018 Alessandro Variola, LAL ORSAY F.Poirier

PHIL - Photoinjecteur au LAL
5/23/2018 Alessandro Variola, LAL ORSAY

Diagnostics Transport Charge : Faraday cup, ICT Énergie : dipole + slit, YAG screen Size: YAG-Ce screen + CCD Position : 2 BPM Bunch length : Cerenkov + streak Emittance : 3 gradients (solenoid), pepper-pot (slits) 5/23/2018 Alessandro Variola, LAL ORSAY

Charge Transport HF 1 m Booster Emittance screen pump RF Gun BPM2 BPM1 Vacuum valve laser Faraday cup slit solenoids Cerenkov 60° dipole 5/23/2018 Alessandro Variola, LAL ORSAY

Charge Charge= f(phase) Max charge: 0.2 nC After dark current substraction 5/23/2018 Alessandro Variola, LAL ORSAY

Energy Transport HF 1 m Booster Emittance screen PUMP RF Gun BPM2 BPM1 Vacuum valve laser Faraday cup slit solenoids Cerenkov 60° dipole 5/23/2018 Alessandro Variola, LAL ORSAY

Energy Dipole measurements Estimated energy: 5 MeV +/- 0.5 MeV good agreement We can increase the resolution with the slit Energy meas.Slit 5/23/2018 Alessandro Variola, LAL ORSAY

Beam size 5/23/2018 Alessandro Variola, LAL ORSAY

Beam Sizes Waist (best set) : 0.5 mm 5/23/2018 Alessandro Variola, LAL ORSAY

Conclusions We found P2I a very effective financing source No red tapes, fast financing for average amounts Thanks to this a lot of work has been done We believe that it was a good success!!!! We propose and studied the baseline positron sources for CLIC and SuperB As far as PHIL is concerned we realized a lot of measurements and we will improve the facility Unfortunately: - Accepted for a request of 90 k Euros - Reduced to 30 kEuros (but we had not a no program reduction plan…) - We did not receive any money, following our administration…are we wrong? 5/23/2018 Alessandro Variola, LAL ORSAY

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