SYNTHESIS OF SUPERHEAVY ELEMENTS USING THE MASS SPECTROMETER MASHA

Transcription

1 SYNTHESIS OF SUPERHEAVY ELEMENTS USING THE MASS SPECTROMETER MASHA Students Timofei Tikhomirov - RB Kevin Li - RSA Alesya Lebedevich - RB Maurice Mashau - RSA Supervisor Krupa Lubosh Flerov Laboratiory of Nuclear Reactions, JINR, Dubna, Russia

2 The main purposes *To measure the alpha decay of Hg and Rn isotopes, produced in fusion reactions: 40 Ar+ nat Sm nat-xn Hg+xn and 40 Ar+ 166 Er 166-xn Rn+xn, in the focal plane of mass spectrometer. *To define the operation speed of the given technique and relative yields of isotopes in the test reactions. *To analyse data acquired from the Medipix2 data and simulate the detector to reproduce some results. *To implement positional tracking alongside energy deposition.

3 (Mass Separator of Heavy Atoms) Mass measurements with accuracy ~ spectroscopy of transuranium nuclei -spectroscopy X-ray spectroscopy Laser spectroscopy

4 Пучок ионов 1 Target box with hot catcher; 2 Ion source; 3 Mass separator; 4 Detector in the focal plane D1 Q1 Q2 D2 General ion-optical parameters: Range of energy variation, kv Range of Br variation, Tm Mass acceptance, % +/-2.8 Angular acceptance, mrad +/-14 Diameter the ion source exit hole, mm 5.0 Horizontal magnification at F1/F2 0.39/0.68 Mass dispersion at F1/F2, mm/% 1.5/39.0 Linear mass resolution at F1 75 Mass resolution at F Q3 S1 D3a D3b S2 Mass-spectrometer MASHA at the beam line of the cyclotron U-400M The proposed setup is a combination of the so-called ISOL method of synthesis and separation of radioactive nuclei with the classical method of mass analysis, allowing mass identification of the synthesized nuclides in the wide mass range.

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6 Testing experiments on heavy ion beams 112 element chemical analog of Hg 114 element chemical analog of Rn

7 Energy of alppha decay [ MeV ] 40 Ar+ 166 Er, E beam = 198 MeV, T catcher =1600 o C 7,6 7,4 7,2 7,0 6,8 6,6 6,4 6,2 6,0 5,8 5,6 5,4 201 Rn (3.8s, 7s) 202 Rn (9.85s) 203 Rn (28s, 45s) 204 Rn (1.24m) 205 Rn (2.83m) counts 2,000 27,00 52,00 77,00 102,0 127,0 152,0 177,0 200,0 5, Strip number

8 counts counts counts counts Po (E kev) 40 Ar Er, Gate on mass A = Rn (E kev) Po (E kev) 40 Ar Er, Gate on mass A = Rn (E kev) E kev 2000 E kev E kev E kev E kev E kev energy [ kev ] energy [ kev ] Po (E kev) 40 Ar Er, Gate on mass A = 203 E 203 Rn (E kev) kev Po (E kev) Ar Er, Gate on mass A = 204 E kev 204 Rn (E kev) E kev E E kev kev energy [ kev ] E kev energy [ kev ]

9 Log10(Po isotopes yield) Log10(Rn isotopes yield) Yields of Rn 5 Yield 4,8 4,6 Beam energy of 40 Ar = 202 MeV 4,4 4,2 4 3,8 3,6 3,4 Yields of Po 3, Mass number, a.m.u. 5,2 5 Yield 4,8 4,6 4,4 4,2 4 3,8 3, Mass number, a.m.u.

10 Log10(Pt isotopes yield) Log10(Hg isotopes yield) Yields of Hg Yield 7 6,5 6 Beam energy of 40 Ar = 202 MeV 5,5 5 4,5 Yields of Pt 4 3, Mass number, a.m.u. 6,5 6 Yield 5,5 5 4,5 4 3, Mass number, a.m.u.

11 Semiconductor single photon pixel hybrid detector MEDIPIX Detector chip Medipix-2 chip Bump-bonding Planar (300, 700, 1000 m thick) silicon pixel detector (also GaAs, CdTe, or n converter) Bump-bonded to Medipix readout chip containing amplifier, discriminator and counter for each pixel.

12 Medipix2 device is composed of 300µm silicon detector It has the dead layer region which is roughly between 200nm and 500nm square pixels each one of 55µm side Medipix mode - Counting of incoming particles Timepix mode - Measurement of particle interaction per arrival time Time over threshold (TOT) Direct measurement in each pixel Medipix2 device will record an event in one or several pixels if the energy deposited by an incoming particle is greater than the threshold energy (>5kev).

13 Radium 224 Radon 220 Polonium 216 Lead 212 Bismuth 212 Thallium 208 Polonium 212 Lead 208

14 Beta spectrum Alpha spectrum Double alpha spectrum

15 Actual Energy of Emitted Beta-particles For beta decay, the energy distribution for betaparticles is The energy efficiency of the detector highly dependent upon detector geometry. The Medipix2 detector registers a maximal count at an energy of approximately 120 kev. We have qualitatively reproduced the detector response from a previous GEANT4 simulation from a current Phd student at JINR (shown below). Detector Response from Emitted Beta-particles

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18 Actual Energy of Emitted Beta-particles Detector Response from Emitted Beta-particles

19 We observe that there are discretized energy peaks that protrude from the otherwise continuous measured energy distribution of beta-particles. After consultation with our supervisor, we hypothesize that this is the result of internal conversion electrons, which would explain the energy discretization.

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22 Position (x, y) versus Energy Deposition Spectra from data 229 Rn 230 Rn 231 Rn 232 Rn

23 Simulation of Position versus Energy Deposition

24 Simulation of Position versus Energy Deposition

25 - Our Supervisor Dr Lubos Krupa and the MASHA team - I. cěk and Hein Fourie