MRI Cryogenic Compressor Halt Control for Cold Head Stability
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Solution Overview
Problem
The existing techniques for controlling cryogenic cooling systems in MRI apparatuses either lead to a short lifespan of the cold head due to excessive temperature fluctuations or result in high power consumption and helium loss, especially when the compressor is halted for extended periods, violating manufacturer-restricted halt limits.
Innovation Solution
A controller is implemented in the MRI apparatus to manage the cryogenic cooling system by intermittently halting the compressor based on pressure thresholds, setting an upper limit for the number of halts within a predetermined period, thereby minimizing temperature changes and reducing operational time while adhering to compressor halt restrictions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the compressor is halted for extended periods to reduce power consumption, then power consumption is reduced, but the cold head temperature fluctuates excessively causing wear and shortened lifespan
Solution Approach 1:
The compressor operates periodically rather than continuously, with halt periods scheduled to occur no more frequently than the manufacturer-specified limits (e.g., every 24 hours or 6 times per hour). This periodic operation reduces overall power consumption while ensuring that temperature fluctuations occur only at acceptable intervals, preventing excessive wear on the cold head.
Solution Approach 2:
The system dynamically adjusts the compressor operation schedule based on manufacturer-specified halt limits. The control system monitors and manages the timing and frequency of halts to optimize power consumption while ensuring that the number of halts within any given period does not exceed the manufacturer's restrictions, thereby balancing energy efficiency with component longevity.
2Use of energy by moving object
If the compressor is halted frequently to reduce power consumption, then power consumption is reduced, but the number of halts exceeds manufacturer restrictions
Solution Approach 1:
The control system dynamically manages compressor halts to comply with manufacturer-specified limits (e.g., maximum 24 halts per day or 6 halts per hour). The system adapts the halt schedule to ensure compliance while still achieving power consumption reduction through strategic halting during periods when the MRI apparatus is not in use.
Solution Approach 2:
The system incorporates feedback mechanisms to monitor and track the number of compressor halts within specified time periods. This feedback ensures that the halt frequency remains within manufacturer restrictions while still allowing for power consumption optimization by adjusting halt timing based on MRI apparatus usage patterns.
3Temperature
If the compressor operation time is extended to minimize temperature changes, then cold head temperature stability is improved, but power consumption increases
Solution Approach 1:
The compressor operates periodically with strategically timed halt periods that coincide with low-usage periods of the MRI apparatus. During these halt periods, temperature stability is maintained at acceptable levels, and when the compressor does run, it operates for extended continuous periods that allow temperature to stabilize, thereby reducing the frequency of start-stop cycles and optimizing power consumption.
4Use of energy by moving object
If the compressor is halted to reduce power consumption, then power consumption is reduced, but helium loss due to boil-off increases
Solution Approach 1:
The compressor is halted periodically during periods when the MRI apparatus is not in use, reducing overall power consumption. The halt schedule is designed to occur infrequently enough (within manufacturer limits) to prevent excessive helium boil-off, while still achieving significant energy savings during extended halt periods.
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 extends the lifespan of the cold head, reduces power consumption, and minimizes helium loss by optimizing the compressor's operation time and frequency, ensuring compliance with compressor halt limits.
Implementation Method 1
a detection unit that detects the pressure in the refrigerant container
Implementation Method 2
gasified helium is condensed and captured on a surface having a very low temperature
Implementation Method 3
a cryo-cooler that cools the cold head
Implementation Method 4
the superconducting magnet, with which a high magnetic field strength can be achieved
Data Source
AI summary
There is provided an MRI apparatus including a superconducting magnet that includes a refrigerant container and a superconducting coil, a cryogenic cooling system with which the superconducting magnet is provided, and a controller that controls the operation of the cryogenic cooling system. The cryogenic cooling system includes a cold head, a cryo-cooler, a compressor that supplies a compressed gas to the cryo-cooler, and a detection unit that detects the pressure in the refrigerant container, the refrigerant container being provided with the cold head, the cryo-cooler, the compressor, and the detection unit. An upper limit value of the maximum number of times of halts of the compressor within a predetermined period of time is set in advance. The controller intermittently halts the compressor within a range in which the pressure detected by the detection unit is equal to or lower than a predetermined upper limit value and performs control such that the number of times of halts of the compressor within the predetermined period of time reaches the upper limit value of the maximum number of times of halts.