OSCAR: a modular low-threshold hodoscope GDS Topical Meeting 2017 Istituto Nazionale di Fisica Nucleare OSCAR: a modular low-threshold hodoscope for low energy nuclear reactions I. Lombardo, D. Dell’Aquila, M. Miranda, M. Vigilante and the NUCL-EX Collaboration Dip. di Fisica, Università di Napoli Federico II & INFN – Sez. di Napoli Univ. Napoli Federico II and INFN – Napoli ivlombardo@na.infn.it Legnaro, 25/01/2017

3α C3N6H6 α d Important: Hodo with particle identification Application fields of low-threshold hodoscopes Hodoscope  wall of detectors with good energy and angular resolution MS Coupling with magnetic spectrometers: angular correlation studies  spectroscopy of particle-emitting states. Example: X(6Li,d)Ya+Z Hodo Univ. Napoli Federico II and INFN – Napoli d 3α α C3N6H6 Coupling with «tagging» detectors: complete kinematic reconstruction  branching ratios of decay in unbound excited states Example: 14N(d,a)12C*3a Hodo Important: Hodo with particle identification

Development of new hodoscopes Application fields of low-threshold hodoscopes Hodoscope  wall of detectors with good energy and angular resolution Coupling with active gas target: Improvement in energy recostruction of high energy ejectiles Example: 2H(X,Y)p and similar, at high energy Hodo Univ. Napoli Federico II and INFN – Napoli Coupling with MF detectors: QT physics Isospin diffusion QT Multi-BU IMNS Example: HI+HIX+12C*3a Hodo Multi-detector array Development of new hodoscopes

Test and Characterization at LNS - INFN A new versatile hodoscope: OSCAR OSCAR: hOdoscope of Silicons for Correlations and Analysis of Reactions Silicon pads, 300 mm (HAM.) Charge PRE  22mV/MeV Two boards  plug and play Strip Si 20 mm (nominal!)  Micron Std. SSSSD  16 strip , 3 mm wide; 0.125 mm interstrip Charge PRE, 16 ch. NET Inst. (45, 90 mV/MeV) Univ. Napoli Federico II and INFN – Napoli Front-End  Analogic Digital one Test and Characterization at LNS - INFN

Nice granularities  30-40 cm Geometries and MC simulations TEST of OSCAR at LNS: 40,48Ca+40,48Ca at 35 A MeV OSCAR was placed at 102 cm from the target, qlab = 52o Univ. Napoli Federico II and INFN – Napoli 4 strip in one pad  geometrical overlap Exp. data  fragment AD in LAB Solid angles  MC simulations + cross check with Rutherford scattering Nice granularities  30-40 cm

Calculated with the real thickness of SSSSD Isotopic resolution and energy thresholds TEST of OSCAR at LNS: 40,48Ca+40,48Ca at 35 A MeV Isotopic identification up to Li Very low thresholds (≈ 1.2 A MeV) Univ. Napoli Federico II and INFN – Napoli Thin dead layer (0.3mm) Negligible effect of electronics on the identification threshold Cross talk levels under control Calculated with the real thickness of SSSSD

Very good  nuclear spectroscopy Energy resolution TEST of OSCAR at LNS: 40,48Ca+40,48Ca at 35 A MeV and a - source Ca+Ca a source Univ. Napoli Federico II and INFN – Napoli Pu-Am-Cm source in DE-E dE ≈ 70 keV FWHM Very good  nuclear spectroscopy

Worsening of I.R. going towards the RD corner A critical point: the SSSSD thickness uniformity Map of the SSSSD thickness  new LNS facility a Source 241Am 2 mm collimator mobile support SSSSD Si + electronics a Univ. Napoli Federico II and INFN – Napoli High non-uniformity (with this peculiar pattern) silicon wafer cut (20 mm!) FUNDAMENTAL aspect  influence isotopic resolution Worsening of I.R. going towards the RD corner

… does the channeling play a role? A critical point: the SSSSD thickness uniformity Map of the SSSSD thickness  new LNS facility We can investigate how the thickness gradient of the large surface SSSSD influence the I. R. Mass spectra  from the DE-E line with an analytical method  Bethe-Bloch formula N. Le Neindre et al, NIM A 490 (2002) 251 Univ. Napoli Federico II and INFN – Napoli t/y Good mass resolution sA only if t/y < 0.3 mm/mm. Mandatory requirement! Energy loss effect, but … … does the channeling play a role?

Tilt is needed! Channeling effects on ultra-thin detectors In the literature  very few studies on channeling effects in ultra- thin Si detectors  important to prevent loss of energy resolution G. Thungstrom et al, NIM A 546 (2005) Channeling (higher residual energy) Si 14.5 mm a 241Am From the difference with respect to a purely gaussian trend:  channeled component about 15% Our SSSSD, 21 mm thick «pixel» Non channeled (gaussian) Univ. Napoli Federico II and INFN – Napoli Tilt is needed!

Further investigations Channeling effects on ultra-thin detectors Estimate of the channeling effect in the SSSSD: 1) By subtraction of the gaussian component (quantitative, but difficulties  Bragg region) 2) By using the skewness g of residual energy spectra (qualitative) Some dependence on the thickness: > thickness  > channeling But at very low thicknesses??? Quasi – flat behaviour? preliminary Univ. Napoli Federico II and INFN – Napoli G. Thungstrom et al, NIM A 546 (2005) Further investigations

QT investigation (barriers, N/Z, etc.) 40,48Ca+40,48Ca at 35 A.MeV results Low energy part of LCP and fragment spectra isotopically resolved (H, He, Li, Be) Univ. Napoli Federico II and INFN – Napoli QT investigation (barriers, N/Z, etc.) 12

Signals of isospin diffusion 40,48Ca+40,48Ca at 35 A.MeV results Low energy part of LCP and fragment spectra  QT emission 48Ca+48Ca 48Ca+40Ca Univ. Napoli Federico II and INFN – Napoli 40Ca+40Ca N/Z1 N/Z2 N/ZQP N/ZQT N/ZMV Signals of isospin diffusion 13

Good correlator for LCP Unbound fragment emission: correlations Use of OSCAR for correlations  complex fragment emission Projectile Target Pre-equilibrium, stopping, compression Flow, expansion Fragmentation Secondary decays Univ. Napoli Federico II and INFN – Napoli 4He+4He correlation LCP correlations possible Due to the limited statistics  4He+4He correlation (8Be) Very nice peak at 92 keV (8Begs) Erel resolution: ≈ 50 keV FWHM Good correlator for LCP 14

Thank you for your attention! Summary and Conclusions Hodoscopes  good candidates to be used as powerful ancillary detectors in a large variety of experiments OSCAR: a new low-threshold and high granularity, modular, hodoscope 20 mm + 300 mm Si Strip – Si pad detector, 5×5 cm2 area Test of the detector performances: mass and energy resolution Problems: gradient of thickness, channeling in ultra-thin detectors Results on QT emission in Ca+Ca collisions at 35 A.MeV 4He+4He correlations with OSCAR  powerful correlator properties Univ. Napoli Federico II and INFN – Napoli Thank you for your attention! 15

Further Slides Univ. Napoli Federico II and INFN – Napoli

Applicazioni a SPES@LNL Alcuni risultati di Fisica – 2 Rapporti isotopici per il QT (selezioni in vpar)  isospin diffusion ISOBARIC RATIO 40Ca+40Ca 48Ca+40Ca 48Ca+48Ca Univ. Napoli Federico II and INFN – Napoli S. Albergo, S. Costa, E. Costanzo, A. Rubbino, Nuovo Cim A 89 (1985) Applicazioni a SPES@LNL 17

Tests e caratterizzazioni ai LNS - INFN Overview di OSCAR OSCAR: Odoscopio di Silici per le Correlazioni e le Analisi di Reazioni Pads di Silici da 300 mm (Ham.) Preamplificatori di Carica 22mV/MeV Due schede  plug and play Strip Si da 20 mm (nominali!)  Micron sct. SSSSD  16 strip da 3 mm; 0.125 mm interstrip Pre di carica a 16 vie NET Inst. (45, 90 mV/MeV) a source spectrum – 300 mm Univ. Napoli Federico II and INFN – Napoli Elettronica Front-End  analogica (per adesso) Tests e caratterizzazioni ai LNS - INFN