Ion Pump Startup Pulsing to Limit Plasma Formation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing ion pumps face difficulties in starting up at pressures above 10−5 mbar due to the formation of intense plasmas, which limits the potential difference between the anode and cathode, leading to inefficient sputtering and increased pressure.
Innovation Solution
An ion pump controller alternates between increasing and decreasing the potential difference between the anode and cathode by applying pulses of power during startup, limiting plasma formation and reducing energy loss to heat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous power is applied to the ion pump during startup, then the pump should operate continuously to evacuate the chamber, but intense plasma formation occurs which limits the potential difference and causes energy loss to heat
Solution Approach 1:
The patent applies periodic pulsed power instead of continuous power during ion pump startup. The controller alternates between applying power to the ion pump and not applying power, creating periodic operation cycles. This periodic action prevents continuous plasma formation while still achieving effective pumping, thereby reducing energy loss to heat while maintaining productivity.
2Productivity
If high potential difference is applied between anode and cathode, then sputtering efficiency should increase, but plasma formation limits the potential difference and causes damage to the ion pump
Solution Approach 1:
The pulsed power operation creates periodic cycles where high potential difference is applied only during power-on phases. During power-off phases, plasma dissipates and the potential difference can be rebuilt to high levels without sustained plasma formation. This allows high sputtering efficiency during active phases while preventing cumulative damage from continuous intense plasma exposure.
Solution Approach 2:
The controller anticipates plasma formation by periodically interrupting power before damage can accumulate. The pulsed operation serves as a preventive measure, cushioning against the harmful effects of intense plasma by limiting its duration and allowing recovery periods, thereby protecting the ion pump from damage while maintaining sputtering efficiency.
3Adaptability or versatility
If the ion pump starts up at pressures above 10−5 mbar, then it should be able to handle higher initial pressures, but intense plasma formation occurs which limits the potential difference
Solution Approach 1:
The pulsed power mode enables the ion pump to start up at higher pressures by preventing continuous plasma formation that would otherwise limit operation. The periodic on-off cycles allow the pump to handle higher initial pressures effectively, expanding the adaptable startup pressure range while avoiding the energy loss to heat that would occur with continuous operation at these pressures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach prevents intense plasma formation, enhances efficiency by reducing energy wastage to heat, and minimizes damage to the ion pump, allowing successful startup at higher pressures.
Implementation Method 1
magnets on opposite sides of the cathode plates generate a magnetic field that is aligned with the axes of the anode cylinders
Implementation Method 2
An electrical potential is applied between the anode and the cathode
Implementation Method 3
the trapped electrons strike the molecule causing the molecule to ionize. The resulting positively charged ion is accelerated by the electrical potential
Implementation Method 4
The resulting positively charged ion is accelerated by the electrical potential between the anode and the cathode toward one of the cathode plates
Implementation Method 5
The positively charged ion is eventually trapped by the cathode and is thereby removed from the evacuated space. Typically, the positively charged ion is trapped through a sputtering event in which the positively charged ion causes material from the cathode to be sputtered into the vacuum chamber of the pump
Data Source
AI summary
An ion pump controller configured to alternate between increasing and decreasing a potential difference between an anode and a cathode of an ion pump multiple times during the starting of pumping.