The Beam-Test Facility (BTF) of the DAΦNE accelerator complex, in the Frascati National Laboratory of the INFN is in operation since 2004 for the high-energy particle and accelerator community. The performance of the BTF is discussed and the plans for the future upgrade of the facility are introduced

Buonomo, B.

Di Giulio, C.

Foggetta, L.

Valente, P.

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DOI 10.1393/ncc/i2017-17069-6Colloquia: IFAE 2016IL NUOVO CIMENTO 40 C (2017) 69The Frascati LINAC beam test facility performances and upgradesB. Buonomo(1), C. Di Giulio(2)(∗), L. Foggetta(1) and P. Valente(2)(1) INFN, Laboratori Nazionali di Frascati -Frascati (Roma), Italy(2) INFN Sezione di Roma - Roma, Italyreceived 17 October 2016Summary. — The Beam-Test Facility (BTF) of the DAΦNE accelerator complex,in the Frascati National Laboratory of the INFN is in operation since 2004 for thehigh-energy particle and accelerator community. The performance of the BTF isdiscussed and the plans for the future upgrade of the facility are introduced.1. – IntroductionThe Beam-Test Facility (BTF) is an infrastracture mainly dedicated to the develop-ment and testing of particle detectors. The experimental hall available for the users is ashielded area of about 25 m2 where the device under test is irradiated with electron orpositron beams produced by the LINAC of the DAΦNE accelerator complex, extractedbefore the injection into the damping ring to a dedicated transfer line.During the test of their devices, the users have also access to various services availablesuch as power supply, networking, gas system, DAQ, vacuum and cryogenics, alignment,magnetic fields.2. – The LINACThe main aim of the LINAC is to produce bunches with ≈ 1010 electrons /positronswith an energy of 510 MeV for the DAΦNE collider. The injector of the DAΦNE accel-erator complex is an S band (2856 MHz) LINAC that alternately produces and acceleratesthe electron and positron beams up to the collider operation energy of 510 MeV. Beforeinjection into the main rings the beams are stored into the accumulator ring for phasespace damping. The LINAC has been designed, built, and installed by TITAN BETA(USA) [1, 2], and is operational since 1997. The Frascati LINAC consists mainly of twoparts. The first part is the low-energy/high-current section made up of five SLAC-type(∗) Email: claudio.digiulio@lnf.infn.itCreative Commons Attribution 4.0 License (http://creativecommons.org/licenses/by/4.0) 12 B. BUONOMO et al.Fig. 1. – Summary of the BTF parameters.3 meters accelerating structures. The maximum achievable energy, on the Positron Con-verter (PC), is 250 MeV, and in operation, with 10 nsec, about 5 A of electron bunchesat the PC, the energy conversion is 220 MeV. The second part is the high-energy/low-current section made up of ten SLAC-type accelerating structures. It can accelerate thepositron bunches emerging by the PC, up to the maximum energy of 550 MeV. TheSLAC-type structures are travelling wave, constant gradient units and are fed by RFpulses, compressed by means of SLED cavities. Four RF stations provide the power bymeans of 45 MW klystrons.3. – The BTFThe BTF is composed of a transfer line driven by a pulsed magnet allowing thediversion of electron or positron bunches that are not injected into the DAΦNE dampingring, with a duty cycle depending on the injection requirements: from a minimum of 20 upto 49 bunches/s [3] are available for users.Two major modes of operations are possible, based on the user needs. The high-intensity mode is operated when the LINAC beam is directly steered in the BTF hallwith a fixed energy (i.e. the LINAC one) and with a reduced capability in multiplicityselection (typically from 1010 down to 104 particles/bunch). The low intensity mode isoperated when the LINAC beam is intercepted in the initial portion of the BTF line by astep Copper target. This produces a secondary beam with a continuous full-span energy(from LINAC energy down to 50 MeV) and multiplicity (down to single particle/bunch)selection range. In the so-called single-particle mode, the particle multiplicity deliveredto the users follows a Poisson distribution.The facility can thus provide tunable electrons and positrons beams in a defined rangeof the different parameters: energy (up to 730 MeV for e− and 530 MeV for e+), charge(up to 1010 e−/ bunch) and pulse length (1.4–40 ns), as summarized in fig. 1.A scheme of the beam transfer line with some pictures of the elements is shown infig. 2.Users of the BTF are provided with diagnostics tools to control the beam parameters.An example is the monitoring of the beam size by means of a pixelized Silicon detector(FitPIX) installed at the exit of the beamline, as shown in fig. 3 for 450 MeV electronsin single-particle mode.THE FRASCATI LINAC BEAM TEST FACILITY PERFORMANCES AND UPGRADES 3Fig. 2. – The layout of the trasfer line from the LINAC to the BTF experimental hall withphotos of the two dipoles, one of the scrapers and one the copper target.Other particles species available for the user are the neutrons and the energy-taggedphotons.The photo-production neutrons source is obtained by the LINAC primary beam onan optimized tungsten target located in a polyethylenelead shielding assembly. Theneutron spectrum emerging from the target has been characterized, showing the expectedevaporation peak at about 1 MeV [5, 6]. The huge prompt photon background is onlyFig. 3. – On the left the BTF beam spot image acquired with a FitPIX detector (by WidePix).The Silicon sensor size is of 14 mm × 14mm and consists of a 255 × 255 pixels matrix, with apixel dimension of 55 μm. On the right side, the 3D image is shown. The best beam obtainedwas σx = 420 μm and σy = 440 μm operating in single-particle mode.4 B. BUONOMO et al.partially reduced by the choice of the 90◦ extraction channel from the lead/polyethyleneshielding.The BTF energy-tagged photons source is an active Bremsstrahlung target. It consistsof two pairs of Silicon single-sided micro-strip detectors to measure the coordinates andthe direction of the electrons beam and to cause the emission of bremsstrahlung photonsbefore last dipole in the BTF hall. A series of modules of Silicon micro-strip detectors,placed in the final dipole pole gap, is used for the measurement of the radiating electronenergy loss and tag the photon energy. The system has been designed in collaborationwith the AGILE [7] (gamma astronomy satellite) team, with the aim of calibrating witha well defined energy and impact point photon beam the scientific payload before thelaunch.4. – The upgrade of LINAC BTFAn important upgrade program of the facility is under evaluation, along three mainlines [8]: consolidation of the LINAC infrastructure, in order to guarantee a stable op-eration on the long term; upgrade of the LINAC energy, in order to increase the facilitycapability (especially for the almost unique extracted positron beam); doubling of theBTF beam-lines, in order to cope with the significant increase of users due to the muchwider range of applications.Consolidation of the LINAC. A LINAC modulators consolidation and the realizationof a complete test of a new RF station is in program. These two different activitiesare strongly related, since the additional RF power station is a fundamental element forpreparation and testing of the components for the consolidation of the existing modula-tors, thus avoiding a very long shut-down of the LINAC.Fig. 4. – The project of the new BTF layout with the doubling of the line.THE FRASCATI LINAC BEAM TEST FACILITY PERFORMANCES AND UPGRADES 5Upgrade of LINAC energy. The energy of the LINAC will be upgraded to 1 GeV,by adding four more accelerating sections which will be supplied by a fifth RF station.A simpler scheme is in project which exploits the extra-length in the LINAC tunnel,of about 15 m, between the last accelerating section at the end of the LINAC and thethree-way switch-yard (towards the damping ring, the BTF and the spectrometer line)as shown in fig. 1, presently used as a drift space, with four quadrupoles to preserve thebeam optics.Doubling BTF line. The possibility to have a second beam-line for the BTF has beenstudied. With the current infrastructure an average of 200 beam-days are delivered toabout 20 experiments in a year. Having a second line will allow to work in parallel andit will be particularly useful in case of long-exposure experiments. A first applicationwill be the PADME experiment for dark photon searches [9]. The INFN has approvedPADME for running at the BTF in late 2017/beginning of 2018, for reaching an exclusionof ε = 10−3 for invisible decays, up to 26 MeV/c2 dark photon masses [10]. Simulationsof the new transfer line with MAD-X and G4-beamline confirm that the new layoutprovided in fig. 4 is compliant to the beam requirements [11,12].5. – ConclusionsThe BTF is continuosly improving and the upgrade program is in progress in order totake into account the increasing user requirements. This ensures that the BTF continuesplaying a key role within the European infrastructures dedicated to development andtest of particle detectors.∗ ∗ ∗This work is supported by the H2020 project AIDA-2020, GA no. 654168. http://aida2020.web.cern.chREFERENCES[1] Sannibale F. et al., DAFNE Technical Note BM-2, April 1997.[2] Buonomo B. et al., IPAC2015, Richmond, USA, May 2015, paper TUPWA056.[3] Foggetta L. et al., IPAC2015, Richmond, USA, May 2015, paper MOPHA048.[4] Foggetta L. et al., IPAC2015, Richmond, USA, May 2015, paper MOPHA049.[5] Quintieri L. et al., IEEE NSS/MIC 2010, 915-919 (2010).[6] Quintieri L. et al., Phys. Procedia, 26 (2012) 249.[7] Cattaneo P. W. et al., Nucl. Instrum. Methods A, 674 (2012) 55.[8] Valente P. et al., INFN-16-04/LNF.[9] Raggi M. et al., EPJ Web of Conferences, 96 (2015) 01025.[10] Bedeschi F. et al., Frascati Physics Series, vol. LX (2015).[11] Buonomo B. et al., AIDA-2020-NOTE-2016-001.[12] Ballerini G. et al., AIDA-2020-NOTE-2016-002.

The Frascati LINAC beam test facility performances and upgrades

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The Frascati LINAC beam test facility performances and upgrades

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