Perfectly matched pulsed 2MHz RF network and CW 30MHz RF matching network for the J-PARC RF-driven H− ion source

Cesiated surface H− ion source: optimization studies

“…The impurity elements causing (4), (6), and (8) were Cs, argon/nitrogen, and H 2 Os, respectively. The impurity element causing (7) seems to be the argon/nitrogen adsorbed on the inner surface of the PCH, since the conditioning of (7) is required for the pre-conditioned and offline-preserved PCHs. The elucidation of the causes of impurity effects by plasma simulations is also expected.…”

“…As shown in figure 3(a), a matching network comprising two COMET CVLI-30 CC /15 -BANs [19], which are vacuum-variable capacitors with a tunable range between 3 and 30 pF and a peak working voltage of 9 kV, is used for the J-PARC source [7]. The RF characteristics of the resonant circuit comprising the network and an RF-antenna are examined with a network analyzer.…”

“…The latter requirements have been satisfied using the superior internal RF-antenna developed at the Spallation Neutron Source (SNS) [3]. Several measures have been implemented to increase the beam brightness [4][5][6][7][8][9][10][11][12][13][14][15][16]. Almost all effective measures were found, in persistent experiments, to reproduce the accidentally produced H − ion beam with the record-breaking smallest emittances.…”

“…(3) axial magnetic-field correction around the PE beam aperture to increase beam intensity by a maximum of 15%, (4) operation at a low PE temperature (T PE ) of about 70°C to reduce ε 95%nrmsx/y by 27%, (5) suitable beam apertures of the plasma and the extraction electrodes to increase beam intensity by a maximum of 7% and to reduce ε 95%nrmsx/y by more than 4%, (6) argon/nitrogen elimination and 39% filter-field reduction to reduce ε 95%nrmsx/y by 9% and the required 2 MHz RF power by around 30%, (7) eight-hours conditioning with a 50 kW 2 MHz RF and a 5% (1 ms×50 Hz) duty factor to reduce ε 95%nrmsx/y by 15%, and (8) slight water molecules (H 2 Os) feeding in hydrogen to avoid ε 95%nrmsx/y increase by 72% and divergence angle expansion by 50%.…”

Emittance measurements for optimum operation of the J-PARC RF-driven H− ion source

“…In the upgrade, the radio-frequency quadrupole linac designed to accelerate 30mA H¯ ion beam (30mA-RFQ) and the cesium (Cs) free H¯ ion source driven with a lanthanum hexaboride (LaB 6 ) filament were replaced with a 50mA-RFQ and a cesiated RF-driven H¯ ion source. The J-PARC new source was developed by using an internal-antenna developed at the spallation neutron source (SNS) [2,3,4,5,6,7,8,9,10], based upon J-PARC prototype sources driven with a LaB 6 or two tungsten (W) filaments [11]. The requirements for the source are an H¯ ion beam of 60mA within normalized emittances of 1.5mm•mrad both horizontally and vertically, a flat top beam duty factor of 1.25% (500s25Hz) and a life-time of longer than 1month.…”