MRTOF mass measurements at GARIS-II: Toward SHE identification via mass spectroscopy
Purpose of SlowSHE 118 Alpha decay 117 Spontaneous Fission Beta Decay / Electron Capture Directly Synthesizable / T <5 ms 1/2 113 Fl 115 Lv 175 Directly Synthesizable / T >5 ms 1/2 Cn Md No Rf Lr Db Sg Bh Hs Mt Ds Rg 160 165 170 Longer half-lives 3-body decay more likely Low rates N= 145 150 155 Already start to see increase in SF Eventually longer T1/2 will become bottleneck, too
SlowSHE Facility LINAC SlowSHE Flat Trap Pulsed Drift Tube
Low-energy beam preparation Very fine wire rf-carpet
Low-energy beam preparation 205 Fr
Low-energy beam preparation ns pulse Continu ous ion bea m μs pulse ns pulse Multi-directional flat rf-trap
Simplified MRTOF Methodology + Ion Trap MCP 0V Approx. Potential
Simplified MRTOF Methodology 1. Accumulate and cool Ions in trap Ion Trap + MCP 0V Approx. Potential
Simplified MRTOF Methodology 1. Accumulate and cool Ions in trap 2. Lower voltage on injection Ion Trap + MCP 0V Approx. Potential
Simplified MRTOF Methodology 1. Accumulate and cool Ions in trap 2. Lower voltage on injection Ion Trap + MCP 3. Eject ions from trap 0V Approx. Potential
Simplified MRTOF Methodology 1. Accumulate and cool Ions in trap 2. Lower voltage on injection Ion Trap + MCP 3. Eject ions from trap 4. Raise voltage on injection 0V Approx. Potential
Simplified MRTOF Methodology 1. Accumulate and cool Ions in trap 2. Lower voltage on injection 0V Ion Trap + MCP 3. Eject ions from trap 4. Raise voltage on injection 5. Wait for N reflections Approx. Potential
Simplified MRTOF Methodology 1. Accumulate and cool Ions in trap 2. Lower voltage on injection 0V Ion Trap + MCP 3. Eject ions from trap 4. Raise voltage on injection 5. Wait for N reflections 6. Lower voltage on ejection Approx. Potential
Simplified MRTOF Methodology t t0 m = m ref t ref t 0 2 1. Accumulate and cool Ions in trap 0V Ion Trap + MCP 2. Lower voltage on injection 3. Eject ions from trap 4. Raise voltage on injection 5. Wait for N reflections 6. Lower voltage on ejection Approx. Potential 7. Detect ions at MCP
Comparison to PTMS r m t tof = L 2K @t tof @K 0 Isochronous! PTMS ~ 304 T m m = Rm=150,000 N 150 δm/m 5x10-7 N 10 δm/m 2x10-6 a R m p N, Slow,
Simultaneous Measurements Counts / 6.4 ns Counts / 6.4 ns Counts / 3.2 ns 165 Ho( 40 Ar, 4n) 201 At 169 Tm( 40 Ar, 4n) 205 Fr 169 Tm( 40 Ar, 3n) 206 Fr Decays or ypxn-channels?
Results: Weighted average mass deviation Reference: 133 Cs + 205 Fr + Species Δm [kev] Δm [kev] N [ions] 201 At -342(45)(3) 522 201g Po -16(74)(3) 108 201 Bi -35(385)(3) 6 205 Fr -80(36)(60) -- 467 205 Rn 212(320) 48 205 At 73(420) 11 205 Po -1059(2050) 2 206m Fr -98(118)(1) 210 206 Rn 551(600)(1) 3 206 At -69(2150)(1) 3 27pSH-6
Mass measurements from first run 2000 1500 1000 m - m AME 12 [kev] 500 0-500 -1000-1500 -2000-2500 -3000 201 Bi 201g Po 201 At 205 Fr 205 Rn 205 At 205 Po 206m Fr 206 Rn 206 At
Next Step: TransFermium nuclei 278 113 277 Cn Projectile Beams 15 N 1 p A 22 Ne 3 p A 40 Ar 1 p A 48 Ca 1 p A 50 Ti 500 pna 54 Cr 272Rg 274Rg 269 Ds 271 Ds 273 Ds 268 Mt 270 Mt 264Hs 265 267 Hs Hs 269 Hs 261Bh 264 266 Bh Bh 244 Fm 3.5 ms 245 Fm 4.2 s 249 Md 251 160 kev 1.0 s 250 52 s 0.8 s 253 30# kev 1.3 s 252 1254 kev 2.54 s 251 4.2 m 0.6 s 0.8 s 255Rf 256 Rf 257 Rf 258Rf 254 17.1 s 253 1.56 m 252 2.3 m 247 248 Fm Fm 249 250 251 Fm Fm Fm 257 Db 140# kev 2.3 s 0.67 s 6.6 ms 255 40 kev 2.5 s 254 N=152 31 s 1295 kev 265 ms 51 s 253 Md 252 Fm 259 Sg 258 Db 60# kev 1.9 s 73 kev 4.3 s 256 255 22 s 3.5 m 4.5 s 4.8 s 260 Sg 4.95 ms 257 Lr 256 6.0 s 2.9 s 261 Sg 183 ms 259 260 Db Db 262Db 259 Rf 258 Lr 257 4.1 s 24.5 s 254 256 Md Md 255 Md 262 Sg 259 Lr 6.2 s 263 Sg 261 Rf 260 Lr 3.0 m 265 Sg Mass measurements of trans-fermium isotopes will provide important data for nuclear shell models used to predict location and properties of the Island of Stability
Deeper into the future... 118 Alpha decay 117 Spontaneous Fission Beta Decay / Electron Capture Directly Synthesizable / T <5 ms 1/2 113 Fl 115 Lv 175 Directly Synthesizable / T >5 ms 1/2 Cn Md No Rf Lr Db Sg Bh Hs Mt Ds Rg 160 165 170 Longer half-lives 3-body decay more likely Low rates N= 145 150 155 Already start to see increase in SF Eventually longer T1/2 will become bottleneck, too
Conclusion Using MRTOF-MS we can: Simultaneous mass measurement Short-lived nuclei Heavy nuclei Identify nuclei with few counts
SlowSHE Facility Initial estimates Process 1. He Gas Cell Stopping Efficiency 60% 2. Ext. via RF-Carpet: 0-5 ms 3. OPIG Transport: < 1ms 4. Ion Cooling: 2 ms 5. MRTOF ToF-MS: 2~10 ms 50% 100% >5% 100% Total 5~20 ms 1%