PoS(ICRC2017)226 , 3 , 4 , M. Lang 3 http://pos.sissa.it/ , G. Tarlé 4 flight detector, and a , B. Kunkler 5 , M. Schubnell ∗ 6 6 , D. Hanna 4 , N. Park 7 , and I. Wisher 6 , N. Green ICRC2017 3 e instrument is scheduled to have a long-duration balloon , S. Nutter 3 Be from 0.2 GeV/n tod3GeV/n, beyon will provide an essential set 10 detector. Th , S. P. Wakely 3 , M. Gebhard 2 , J. Musser 6 scientific goals and the design of the experiment, and report on its current , G. Visser , S. Coutu 4 1 , D. Müller 2 superconducting magnet with a high-resolution tracking system, time of ring-imaging Cherenkov by HELIX, especially of HELIX (High Energy Light Isotope eXperiment) issure a the balloon-borne experiment chemical designed and to mea- isotopic abundances of light cosmic ray nuclei. Detailed measurements of data for the study of propagation processes of the cosmic rays. HELIX consists of a 1 Tesla flight out of McMurdo Station during NASA’s 2019/20 Antarctic balloon campaign. Instatus. this talk, Speaker. we will discuss the ∗ Copyright owned by the author(s) under the terms of the Creative Commons c Bexco, Busan, Korea 10–20 July, 2017 35th International Cosmic Ray — Conference Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). Cosmic-ray isotope measurements with HELIX McGill University, Montreal, Canada University of Chicago, Chicago, IL 60637Northern USA Kentucky University, Highland Heights, KY 41099 USA The Ohio University, Columbus, OH 43210Pennsylvania USA State University, University Park, PA 16802Indiana USA University, Bloomington, IN 47405 USA University of Michigan, Ann Arbor, MI 48109 USA J. J. Beatty I. Mognet A. Tomasch 5 6 7 1 2 3 4 PoS(ICRC2017)226 6 )) ]. − 7 , 6 + e N. Park + /(e + Be ratio, to energies Be ratio can be used, 9 9 Be), which decays with Be/ 10 Be/ 10 10 Be is entirely determined by the 9 Be measurements can also provide 9 Be/ 10 GeV/n. HELIX will be able to make 10 ∼ Be to stable 3 GeV/n) between entire classes of propagation 1 10 ∼ –decay isotope beryllium-10 ( ]. High-quality β 3 , 2 , 1 ] 5 , 4 , 2 Also, the abundance measurements of other stable isotopes serve complementary roles to study The importance of propagation studies of the cosmic rays has become more vital as recent Understanding the sources and acceleration mechanisms of the cosmic rays has been one of Abundance ratios of radioactive isotopes with known decay times can provide a direct mea- To address the questions related to the interpretation of these unexpected observations, im- propagation history of the cosmic rays. In diffusion halo models, the strong discrimination (especially at energies of the propagation of cosmic rays. Theytion provide key histories, tests by of examining the species ’universality’ with of different cosmic-ray Z/A propaga- ratios and overall abundance levels [ measurements reveal interesting new cosmic-ray properties. Forshow example, spectral several index elemental hardening spectra around 200 GV,which wasrecent not expected. result The has most highly been publicized the remarkable increase observed in the positron fraction (e a half-life of 1.39 Myr.rays Because with beryllium the is interstellar mainly medium, produced by the interactions ratio of of together heavier with cosmic constraints from stable secondary-to-primarysion ratios, coefficient to and estimate the values halo for size the [ diffu- models [ precise measurements of important isotopic abundances, including the the main goals of astroparticle physics forto more understand than a how hundred particles years. propagate To achieveobservable from this to goal, their study we the source need propagation sites is to theto-carbon elemental the (B/C) secondary-to-primary ratio. Earth. ratio, Based such A on as commonly the theabundance assumption selected boron- of that the the local cosmic-ray elemental source abundancethat sites, is those similar an ’secondary’ particles to over-abundance are the of generated by particlesrelative spallation such abundance interactions during as of the secondary boron propagation. particles indicates The toof primary the particles probes cosmic the rays total overprimary material their ratios path containment are length indispensable time to before unravel cosmic-ray theyare histories reach insufficient of the propagation, to they Earth. fully by themselves constrain Whileexample, they all secondary-to- are parameters. sensitive only In tolarge the the degeneracies ratio case in the of of parameter the diffusion space. halo models size with to the halos, diffusion for coefficient,surement leading to of the containmentthe time most of important cosmic such rays, isotopes is removing the some of the degeneracies. One of proving the measurements thatEnergy permit Light studies Isotope of cosmic-ray eXperimentmeasure propagation (HELIX) light is is isotopes essential. a from 0.2 new The GeV/n long-duration eventually High balloon up to payload designed to Cosmic-ray isotope measurements with HELIX 1. Introduction reported by the PAMELA, AMS-02 and Fermi/LAT collaborations.traditional This behavior models is of in conflict cosmic-ray with physicsincluding and particle has production been in attributed nearby to astrophysicalsources, a including objects, wide the propagation variety annihilation physics, of or or phenomena, decay more of exotic dark matter particles. over an order of magnitudestudy higher the than propagation. previously achieved, providing essential measurements to PoS(ICRC2017)226 6 2.5% ∼ N. Park 30 V), so the m spatial res- µ ∼ ]. 8 , the major components of 1 . These specifications provide 3 3 GeV/n [ − ∼ 10 × 1 ∼ β / β ∆ 2 Be measurements up to 9 Be/ 10 5 GeV/n. The combination of the time-of-flight system and the ∼ 4 GeV/n with a velocity resolution of ∼ Partially sectioned 3D model of the High Energy Light Isotope eXperiment detector sys- Be measurements up to The HELIX instrument is a magnet spectrometer designed to measure the light isotopes, es- With the 1 T magnetic field provided by the superconducting magnet and 65 One of the challenges is to make an efficient readout under a 1 T magnetic field. Traditional 10 sr and up to 14 days of flight time, HELIX is sufficient to pursue high-statistics measurements 2 the mass resolution needed for the olution provided by the gasfor tracking system, HELIX canring achieve imaging a Cherenkov detector rigidity system resolution willGeV/n of allow up HELIX to to cover a wide energy range from 0.2 pecially focusing on the isotopes of beryllium. As shown in Figure photomultiplier tubes (PMTs) become inefficientmagnetic under shielding strong or magnetic delicate fields fieldsilicon and alignments. photomultiplier require (SiPM) heavy HELIX readout utilizes insteadtection the of efficiency most PMT and recent readout. an development SiPMs of special excellent provide shielding. single a photoelectron The high resolution bias photode- under voltage magnetic required field for SiPM without operation is much lower ( Figure 1: tems, showing superconducting magnet, driftCherenkov detector. chamber tracker, two time-of-flight layers and ring-imaging the instrument, besides the magnet, arement, the a scintillator drift paddles chamber on tracker, the a topinstrument bore and is paddle, bottom designed and of to a the fly ring instru- onm imaging a Cherenkov long-duration Detector. balloon The flight. HELIX Withof a isotopic geometric ratios acceptance even of at 0.1 high energy. readout does not suffer from the same kind of high-voltage corona problem frequently encountered Cosmic-ray isotope measurements with HELIX 2. Instruments PoS(ICRC2017)226 6 ]. 9 N. Park focal plane will consist of an m for Z>3 particles by utiliz- 2 µ . Because the RICH will have low 65 2 ∼ 6 mm × 1 kV/cm, and high-speed sampling readout ∼ 3 1 GeV/n), and expansion length 500 mm. The 1.32 m ∼ 1 GeV/n and the charge of the particles from proton up to neon (Z=10). It consists of ∼ The bore of the magnet will house a drift chamber tracker (DCT) to continuously track parti- A brief description of the main components follows: The superconducting magnet that will be used for HELIX can provide an approximately uni- The HELIX time-of-flight (TOF) and charge system will measure the velocity of the particles For measurements of particle velocities at high energy, where the TOF system cannot provide a cles through the magnetic field.tracker’s To size, minimize the the DCT source utilizes ofwill the Coulomb employ entire scattering a and tracking flat-geometry maximize volume design the as withThe a 72 DCT sense multi-wire is layers, drift designed segmented chamber. to into achieve three HELIX a drift mean cells spatial per layer. resolution of 2.2 Drift Chamber Tracker 2.1 Superconducting Magnet form 1 T fieldcryostat within axis are a immersed rectangular in a warmtemperature liquid-helium (LHe) bore. of bath 9.8 to keep Two K. the superconducting Theof temperature below approximately LHe coils the seven capacity centered critical days. of The along the magnetdesigned the was magnet for built is the by HEAT 260 Cryomagnetics experiment. Incorporated liters, It and has which originally been provides used a in five hold successful time balloon campaigns [ Cosmic-ray isotope measurements with HELIX with PMTs. However, thermal noise, also knownthe as performance dark has current, strong is correlation much with higher theHELIX than temperature readout of in system the PMTs requires device. and a For careful stableambient thermal operation, temperature the design monitoring. and a compensation system based on the ing low-diffusion drift gas, a moderate drift field of array of 64-channel Hamamatsu SiPMs with pixelpixel size photon 6 occupancies (average photons per pixel <3 for Z=4), it is important to minimize the up to two layers of 1.5-cminstrumentation thick stack, fast with plastic a scintillator totalbe paddles, separation read of located out by 2.3 at three m. the SiPMexpect at The top the each paddles and TOF each will of system bottom each be to of paddleTOF 1.6 achieve Using the a system m the timing and long, planned resolution a 10 and of psec bore will system-wide TDC <50 paddle, trigger. system, ps a we for small Z>3. scintillator The paddle combination located of under the the2.4 DCT, will Ring provide Imaging a Cherenkov Detector discriminating measurement, HELIX will use a proximity-focuseddetector aerogel ring (RICH). imaging On Cherenkov the basislowing of configuration: extensive GEANT4 10 Monte mm Carloenergy thickness simulations, of aerogel we adopt radiator the with fol- refractive index of 1.15 (threshold electronics. The DCT will bethe placed magnet inside to a maintain 1 pressurized atm vessel pressure that during tightly the fits flight. inside2.3 the Time-of-Flight bore and of Charge System PoS(ICRC2017)226 6 N. Park Be ratio 9 Be nuclei. 10 Be/ 10 2.5% from 0.2 GeV/n ∼ Be nuclei and 9 ]. Also shown on the plot are the results 4 . In addition to the results from the 14-day Be nuclei from a few hundred MeV/n all the 2 10 shows the expected relative mass resolution of 4 ]. Be nuclei. This plot is based on full Monte Carlo 2 10 10 Be ratio, reaching with good statistics well into the region where time 9 Be/ -weighted contribution from the velocity-determining instrument: the TOF below 1 2 10 γ Left: Predicted relative mass resolution vs. energy per nucleon for the HELIX instrument with 4 GeV/n, which corresponds to 0.3 a.m.u. separation between ∼ 3 GeV/n. The charge of incident particles will be measured for protons (Z=1) up to neon The black line in the left panel of Figure HELIX is designed to measure the mass of nuclei with a resolution of ∼ Be incident particles. The blue line is the contribution to the mass resolution from the spectrometer; With 14 days of Antarcticmeasurements flight, in HELIX the will low provide energies data and1.1-2.0 well that GeV/n beyond can the as be low-statistics shown compared measurement in with by the ISOMAX ACE/CRIS right at panel of Figure way to of ACE/CRIS (triangles) and ISOMAX (squares). simulations based on the instrument configurationcan provide described less above. than 3% As relative shown mass in resolution the for plot, HELIX flight discussed here, expected results fromare a also future 28-day shown. exposure in Clearly,the an even upgraded behavior configuration the of initial the HELIX results will provide very strong constraints on HELIX versus kinetic energy per nucleon for Figure 2: 10 the green line is the GeV/n and the RICH aboveberyllium 1 isotope GeV/n. ratio measured The by black HELIX. Thethe line blue instrument is crosses configuration the show described results quadrature for here. sum aan The of 14-day upgraded Antarctic green the instrument. flight dots two. with The show Right: results bluethe for line Anticipated red a represents line future a represents 28-day Leaky a exposure Box diffusion halo with model model with with a re-acceleration low-density [ Local Bubble and 3. Expected Performance and Results to (Z=10) by complementary detectors–the TOF andcan RICH provide good systems. mass With separation this for performance, adjacent HELIX light isotope measurements. Cosmic-ray isotope measurements with HELIX dark counts from the SiPMs.the We will focal accomplish plane this will by be coolinglowers the partially the focal populated velocity plane. with resolution To sensors of reduceup arranged costs, the to in device, about a 4 but GeV/n. checkerboard still The pattern. enablesother details measurements HELIX of This contribution of the in RICH the this design conference and [ testing for HELIX can be found from the PoS(ICRC2017)226 6 N. Park 8 GeV/n because the relative ∼ ]. HELIX will also measure the light 11 5 ICRC proceeding ICRC proceeding Be ratio, HELIX will measure several other important isotopic abun- th 9 th ICRC proceeding Be/ th 10 Be nuclei are expected above 2 GeV/n, an area where no measurements currently exist. He ratio, HELIX can provide good measurements up to 4 10 He/ 3 Up to now, we have focused on the finalization of the detector design, including the selection In addition to the [9] J. J. Beatty et al., 2004, Phy. Rev. Lett. 93, 241102 [1] J. A. Simpson & M. Garcia-Munoz,[2] 1988, SpaceM. Sci. Simon, Rev. 46, 1999, 205 27 [3] A. W. Strong et al., 2007,[4] Annual Review ofT. Hams Nuclear et and al., Particle Science 2004, 57, ApJ[5] 285 611, 892 A. Putze et al., 2010, A&A[6] 516, A66 B. Coste et al., 2012, A&A[7] 539, A88 N. Tomassetti, 2012, Ap&SS 342, 131 [8] S. Wakely et al., 2015, 34 [10] I. Wisher et al., 2017, 35 of SiPMs based onFor their this, performance we have test developed smaller andoverall scale simulation, design. prototype detectors and Now to selection we test are theintegration of performance moving in the and toward 2018. evaluate readout flight-ware After production system. environmentballoon aiming and flight to ground out start tests, of the we McMurdo Station instrument are during planning NASA’s 2019/20 to Antarctic have balloon a campaign. long-duration References elementary particle fluxes up to 800 GV. 4. Current status and plan [11] N. Prantzos, 2012, A&A 542, A67 Cosmic-ray isotope measurements with HELIX dilation significantly affects the radioactivethan isotope 1500 lifetime. From this 14-day flight alone, more mass difference between these lighter isotopesto-primary is ratio large. or secondary-to-secondary These ratio, isotopicagation can measurements, process. secondary- provide unique Furthermore, information isotope about abundanceproperties the ratios such are prop- as condensation not temperature subject or tocial first modification information ionization by potential, on atomic and the thus can origin provide of cru- cosmic-ray particles [ dance ratios for light elementsas from the proton up to neon. For isotopes lighter than beryllium, such