Design of a high-bunch-charge 112-MHz superconducting RF photoemission electron source.

High-bunch-charge photoemission electron-sources operating in a continuous wave (CW) mode are required for many advanced applications of particle accelerators, such as electron coolers for hadron beams, electron-ion colliders, and free-electron lasers. Superconducting RF (SRF) has several advantages over other electron-gun technologies in CW mode as it offers higher acceleration rate and potentially can generate higher bunch charges and average beam currents. A 112 MHz SRF electron photoinjector (gun) was developed at Brookhaven National Laboratory to produce high-brightness and high-bunch-charge bunches for the coherent electron cooling proof-of-principle experiment. The gun utilizes a quarter-wave resonator geometry for assuring beam dynamics and uses high quantum efficiency multi-alkali photocathodes for generating electrons.

Syntheses and structural characterization of dinuclear and tetranuclear iron(III) complexes with dinucleating ligands and their reactions with hydrogen peroxide.

The iron(III) complexes [Fe(2)(HPTB)(mu-OH)(NO(3))(2)](NO(3))(2).CH(3)OH.2H(2)O (1), [Fe(2)(HPTB)(mu-OCH(3))(NO(3))(2)](NO(3))(2).4.5CH(3)OH (2), [Fe(2)(HPTB)(mu-OH)(OBz)(2)](ClO(4))(2).4.5H(2)O (3), [Fe(2)(N-EtOH-HPTB)(mu-OH)(NO(3))(2)](ClO(4))(NO(3)).3CH(3)OH.1.5H(2)O (4), [Fe(2)(5,6-Me(2)-HPTB)(mu-OH)(NO(3))(2)](ClO(4))(NO(3)).3.5CH(3)OH.C(2)H(5)OC(2)H(5).0.5H(2)O (5), and [Fe(4)(HPTB)(2)(mu-F)(2)(OH)(4)](ClO(4))(4).CH(3)CN.C(2)H(5)OC(2)H(5).H(2)O (6) were synthesized (HPTB = N,N,N',N'-tetrakis(2-benzimidazolylmethyl)-2-hydroxo-1,3-diaminopropane, N-EtOH-HPTB = N,N,N',N'-tetrakis(N' '-(2-hydroxoethyl)-2-benzimidazolylmethyl)-2-hydroxo-1,3-diaminopropane, 5,6-Me(2)-HPTB = N,N,N',N'-tetrakis(5,6-dimethyl-2-benzimidazolylmethyl)-2-hydroxo-1,3-diaminopropane). The molecular structures of 2-6 were established by single-crystal X-ray crystallography. Iron(II) complexes with ligands similar to the dinucleating ligands described herein have been used previously as model compounds for the dioxygen uptake at the active sites of non-heme iron enzymes. The same metastable (mu-peroxo)diiron(III) adducts were observed during these studies. They can be prepared by adding hydrogen peroxide to the iron(III) compounds 1-6. Using stopped-flow techniques these reactions were kinetically investigated in different solvents and a mechanism was postulated.