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)Ya+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+HIX+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