Nonuniform radiation damage in permanent magnet quadrupoles.
C R Danly1, F E Merrill1, D Barlow1
1Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA.
The Review of Scientific Instruments
|September 1, 2014
Summary
Radiation damage causes uneven magnetization loss in neodymium-iron-boron permanent magnet quadrupoles. This degradation, observed in proton radiography facilities, affects magnetic lens performance and image quality.
Area of Science:
- Materials Science
- Particle Accelerator Technology
- Physics
Background:
- Permanent magnet quadrupoles are crucial for particle beam focusing in facilities like the proton radiography (pRad) at Los Alamos and GSI-Darmstadt.
- High neutron fluences near magnets can arise from proton beam interactions with collimators, posing a risk to magnetic lens integrity.
- Previous damage assessments focused on uniform strength reduction, not localized magnetization loss.
Purpose of the Study:
- To investigate the effects of radiation damage on neodymium-iron-boron permanent magnet quadrupoles.
- To understand the non-uniform nature of magnetization loss and its impact on magnetic field quality.
- To correlate observed image degradation in pRad experiments with specific magnet damage mechanisms.
Main Methods:
- Analysis of magnetization loss in permanent magnet quadrupoles subjected to radiation.
- Utilizing proton radiography (pRad) data to assess magnetic lens performance degradation.
- Examining the spatial distribution of magnetization loss within the magnets.
Main Results:
- Data indicate nonuniform magnetization loss in neodymium-iron-boron permanent magnet quadrupoles due to radiation damage.
- Preferential degradation occurs in regions of highest magnetic field intensity.
- Observed damage leads to increased high-order multipole components, degrading magnetic field quality.
Conclusions:
- Radiation damage causes localized magnetization loss in permanent magnet quadrupoles, exceeding expected uniform strength reduction.
- This non-uniform damage directly contributes to image degradation in particle radiography systems.
- Understanding this phenomenon is critical for designing radiation-hardened magnetic systems for accelerators.
Related Concept Videos
01:27Magnetic Fields
5.9K
A moving charge or a current creates a magnetic field in the surrounding space, in addition to its electric field. The magnetic field exerts a force on any other moving charge or current that is present in the field. Like an electric field, the magnetic field is also a vector field. At any position, the direction of the magnetic field is defined as the direction in which the north pole of a compass needle points.
A magnetic field is defined by the force that a charged particle experiences...
A magnetic field is defined by the force that a charged particle experiences...
5.9K
01:23Atomic Nuclei: Nuclear Relaxation Processes
1.1K
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis.
1.1K
01:24Potential Due to a Magnetized Object
922
Magnetic dipoles in magnetic materials are aligned when placed under an external magnetic field. For paramagnets and ferromagnets, dipole alignment occurs in the direction of the magnetic field. However, the dipoles align opposite to the field in the case of diamagnets. This state of magnetic polarization due to the external field is called magnetization. Magnetization is defined as the dipole moment per unit volume. It plays a similar role to polarization in electrostatics.
The vector...
The vector...
922
01:30Paramagnetism
2.4K
Paramagnets are materials with unpaired electrons that possess a finite magnetic moment. In the absence of a magnetic field, these moments are randomly oriented, and thus the net moment is zero. Under an external field, a torque acting on the moments tends to align them along the field's direction. However, the random thermal motion of electrons produces a torque opposite to the external field and tries to disorient the moments. These two competing effects align only a few moments along the...
2.4K
01:23Magnetic Field due to Moving Charges
11.3K
A stationary charge creates and interacts with the electric field, while a moving charge creates a magnetic field.
Consider a point charge moving with a constant velocity. Like the electric field, the magnetic field at any point is directly proportional to the magnitude of the charge and inversely proportional to the square of the distance between the source point and the field point. However, unlike the electric field, the magnetic field is always perpendicular to the plane containing the line...
Consider a point charge moving with a constant velocity. Like the electric field, the magnetic field at any point is directly proportional to the magnitude of the charge and inversely proportional to the square of the distance between the source point and the field point. However, unlike the electric field, the magnetic field is always perpendicular to the plane containing the line...
11.3K
01:28Magnetostatic Boundary Conditions
1.9K
An electric field suffers a discontinuity at a surface charge. Similarly, a magnetic field is discontinuous at a surface current. The perpendicular component of a magnetic field is continuous across the interface of two magnetic mediums. In contrast, its parallel component, perpendicular to the current, is discontinuous by the amount equal to the product of the vacuum permeability and the surface current. Like the scalar potential in electrostatics, the vector potential is also continuous...
1.9K