Producing persistent, high-current, high-duty-factor H- beams for routine 1 MW operation of Spallation Neutron Source...

Area of Science:

• Nuclear Physics
• Materials Science
• Accelerator Technology

Background:

• The Spallation Neutron Source (SNS) operates at 1 MW beam power.
• Extraction of 50 mA H(-) ions is crucial for SNS operation.
• A 5% duty factor is maintained for the H(-) ion beams.

Purpose of the Study:

• To review fundamental processes governing H(-) beam persistence.
• To elucidate the role of cesium in maintaining ion beam current.
• To understand the required operating temperature for the cesium collar.

Main Methods:

• Review of fundamental physical and chemical processes.
• Analysis of operational data from the Spallation Neutron Source.
• Thermodynamic and surface interaction modeling (implied).

Main Results:

• H(-) beam current of 50 mA is sustained for 4-week operational cycles.
• Cesium dose and collar temperature (∼170 °C) are critical for initial beam achievement.
• Mechanisms for sustained H(-) production without continuous cesium supply are identified.

Conclusions:

• The persistence of SNS H(-) beams is attributed to underlying physical processes, not just continuous cesium supply.
• Maintaining the cesium collar temperature near 170 °C is essential for efficient H(-) generation and beam stability.