Electrons Emitted from 33-TeV Pb Ions During Penetratiaon of Solids

Conference · Thu Jul 22 04:00:00 EDT 1999

OSTI ID:10476

Datz, S ^[1]; Grafstroem, P; Knudsen, H; Krause, H F; Mikkelsen, U; Moeller, S; Scheidenberger, C; Schuch, R H; Uggerhoj, E; Vane, C R; Vilikazi, Z

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1. ORNL

At ultrarelativistic energies, ionization cross sections exceed electron capture cross sections by several orders of magnitude (1,2). Effectively, all electrons transferred to a highly relativistic heavy ion moving in a solid or gaseous target medium are stripped in a relatively short distance. Above ~20 GeV/nucleon, the principal mechanism for electron capture is from pair production (ECPP) (2). The total cross sections for ECPP are te&nically important for making reliable predictions of operating limitations for relativistic heavy-ion colliders, e.g., RHIC and LHC (3). In ECPP, it is expected that ~30% of capture proceeds to excited states of the capturing ion. Some of these relatively weakly bound electrons are radiatively long-lived and easily lost in secondary collisions in solid targets, making measurements of their contributions to total capture experimentally difficult. Electrons lost from high-energy ions in collisions with target atoms form a cusp-shaped spectral peak in the forward direction in the laboratory frame centered at the velocity of the moving ion (4-5). The shape of this electron loss to projectile continuum (ELC) peak has been shown (5,6) to depend on the initial atomic bound state from which the electron is ionized. We have measured and compared ELC electrons from direct ionization of hydrogenlike 33-TeV Pb⁸¹⁺(ls) ions (Lorentz factory g = 168) in Al with similar data for electrons created by ECPP for bare Pb⁸²⁺ ions in Au - followed by ionization. Both measured ELC peaks are narrow in momentum and angle and very similar in shape.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN
• Sponsoring Organization: USDOE Office of Science
• DOE Contract Number: AC05-96OR22464
• OSTI ID: 10476
• Report Number(s): ORNL/CP-104602; KC 03 01 03 0; ON: DE00010476
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
Aluminium
Electron Emission
Gold
Ion Collisions
Lead Ions
TeV Range 10-100