ENTRY O1065 20030710 0000O106500000001 SUBENT O1065001 20030710 0000O106500100001 BIB 13 77 O106500100002 TITLE Large enhancement of the sub-barrier fusion probabilityO106500100003 for a halo nucleus O106500100004 AUTHOR (M.Trotta, J.L.Sida, N.Alamanos, A.Andreyev, O106500100005 F.Auger, D.L.Balabanski, C.Borcea, N.Coulier, O106500100006 A.Drouart, D.J.C.Durand, G.Georgiev, A.Gillibert, O106500100007 J.D.Hinnefeld, M.Huyse, C.Jouanne, V.Lapoux, A.Lepine, O106500100008 A.Lumbroso, F.Marie, A.Musumarra, G.Neyens, S.Ottini, O106500100009 R.Raabe, S.Ternier, P.Van Duppen, K.Vyvey, C.Volant, O106500100010 R.Wolski) O106500100011 INSTITUTE (2FR SAC) DSM/DAPNIA, CEA SACLAY O106500100012 (2ITYNAP) and INFN Sezione di Napoli O106500100013 (2BLGLEU) IKS O106500100014 (3RUMPIT) O106500100015 (2BLGLVN) Centre de recherche du cyclotron O106500100016 (1USAISB) Physics department O106500100017 (3BZLUSP) O106500100018 (3POLIFJ) O106500100019 REFERENCE (J,PRL,84,2342,2000) O106500100020 SAMPLE The uranium targets consist of U-F4 deposited on a thinO106500100021 carbon foil of 30 microgramm/cm**2 by thermal O106500100022 evaporation out of a tantalum crucible. The target O106500100023 thickness was 800 microgramm/cm**2 which is equivalent O106500100024 to a 600 microgramm/cm**2 of pure U target. The O106500100025 uncertainty of the thickness is estimated to be 10% andO106500100026 the inhomogeneity of the target is 3%. O106500100027 MONITOR (92-U-238(A,EL)92-U-238,,DA) O106500100028 (92-U-238(2-HE-6,EL)92-U-238,,DA) O106500100029 The monitor reactions were used for high intensities. O106500100030 DETECTOR (COIN,SIBAR,SIBAR) The setup provides an energy O106500100031 measurement of particles with a large angular coverage.O106500100032 It is composed of two open cubes placed on each side ofO106500100033 the target. The faces perpendicular to the beam have O106500100034 been removed to let the beam pass through. Each face O106500100035 is composed of a set of four silicon detectors with a O106500100036 surface of 50 X 50 mm**2 and a thickness of 500 O106500100037 micrometer. The mechanics and the electronics have O106500100038 been constructed with special care in order to reduce O106500100039 the dead zones. The angular coverage is of the order O106500100040 of 70% of 4pi. The measurement of two particles O106500100041 emitted back to back has been optimized by a symmetric O106500100042 design with respect to the target point. The high O106500100043 granularity of 32 detectors allows the measurement of O106500100044 three particles in coincidence with a low pileup O106500100045 probability. Coincidence of two detectors provides theO106500100046 major trigger for the acquisition. O106500100047 FACILITY (CYCLO,2BLGLVN) The experiment was performed at O106500100048 Cyclone, the Radioactive Nuclear Beam facility O106500100049 METHOD (EXTB) O106500100050 (SITA) See SAMPLE O106500100051 (BCINT) The beam intensity was measured during the O106500100052 experiment by a NE102 plastic scintillator placed at 0 O106500100053 degree for beam intensities less than 7.E+05 pps. O106500100054 (EDEG) Intermediate energies have been obtained using O106500100055 mylar absorbers of thicknesses 25 and 50 micrometers. O106500100056 (ABSFY) O106500100057 ADD-RES Energy spectra obtained in the silicon detectors. O106500100058 HISTORY (20030708C) O106500100059 (20030710U) Last checking has been done. O106500100060 ERR-ANALYS (ERR-S) The statistical uncertainties are not directlyO106500100061 correlated to the total number of fissions since the O106500100062 cross sections have been determined on the basis of theO106500100063 number of fissions in each back-to-back pair of O106500100064 detectors and taking into account their measured O106500100065 efficiency. O106500100066 (ERR-1) The systematic uncertainty due to the target O106500100067 thickness. O106500100068 (ERR-2) The systematic uncertainty due to the O106500100069 efficiency of detection. O106500100070 The systematic uncertainties could affect only the O106500100071 global normalization but not the relative cross O106500100072 sections since all the measurements have been performedO106500100073 under similar conditions O106500100074 COMMENT - By authors. The data lead us to conclude that at theO106500100075 barrier no hindrance due to the breakup of the nucleus O106500100076 is observed, and below the barrier there is a large O106500100077 enhancement of the fusion probability for the 6-He O106500100078 nucleus with respect to the stable 4-He nucleus. O106500100079 ENDBIB 77 0 O106500100080 COMMON 2 3 O106500100081 ERR-1 ERR-2 O106500100082 PER-CENT PER-CENT O106500100083 10. 8. O106500100084 ENDCOMMON 3 0 O106500100085 ENDSUBENT 84 0 O106500199999 SUBENT O1065002 20030710 0000O106500200001 BIB 4 4 O106500200002 REACTION (92-U-238(A,F),,SIG) O106500200003 REL-REF (A,C0708002,V.E.VIOLA+,J,PR,128,767,1962) O106500200004 MISC-COL (MISC) Number of fissions detected O106500200005 FLAG (1.) The beam energy has been obtained using absorber. O106500200006 ENDBIB 4 0 O106500200007 NOCOMMON 0 0 O106500200008 DATA 5 6 O106500200009 EN-CM DATA ERR-S MISC FLAG O106500200010 MEV MB MB NO-DIM NO-DIM O106500200011 22.6 200.1 20.5 18059. O106500200012 21.6 93.9 9.5 6074. 1. O106500200013 20.7 33.6 3.6 1324. 1. O106500200014 19.6 4.8 0.3 1525. O106500200015 18.5 0.87 0.08 194. 1. O106500200016 17.4 0.06 0.01 51. 1. O106500200017 ENDDATA 8 0 O106500200018 ENDSUBENT 17 0 O106500299999 SUBENT O1065003 20030710 0000O106500300001 BIB 3 3 O106500300002 REACTION (92-U-238(2-HE-6,F),,SIG) O106500300003 MISC-COL (MISC) Number of fissions detected O106500300004 FLAG (1.) The beam energy has been obtained using absorber. O106500300005 ENDBIB 3 0 O106500300006 NOCOMMON 0 0 O106500300007 DATA 5 8 O106500300008 EN-CM DATA ERR-S MISC FLAG O106500300009 MEV MB MB NO-DIM NO-DIM O106500300010 28.7 1381. 99.1 241. O106500300011 27.7 1480.1 84. 350. 1. O106500300012 26.6 1140.7 71.4 296. 1. O106500300013 25.3 1033.5 33.8 1134. O106500300014 24.2 794.2 36. 570. 1. O106500300015 23. 482. 30.9 268. 1. O106500300016 17.5 37.3 2.2 301. O106500300017 14.6 5.4 0.4 267. O106500300018 ENDDATA 10 0 O106500300019 ENDSUBENT 18 0 O106500399999 ENDENTRY 3 0 O106599999999