The First Comprehensive Measurements Of Particle Beam

• A new method generates the first measurement of all 6 parameters of a particle beam. 
• This will help scientists build efficient, high-powered particle accelerators. 

Particle accelerators are machines that use electromagnetic fields to propel charged or neutral particles to near speed of light. They are used in several fields, including high-energy physics research and cancer treatment.

Particle beams have been studied and refined for many decades. Numerous proposed applications require intensities up to 100 times higher than those of current instruments.

However, it’s quite difficult to accurately predict the distribution of particle beam in a hadron linear accelerator. Their properties are exceptionally tricky to characterize all at once, which limits our ability to design and optimize the existing and future accelerators.

Now, a team of researchers at the University of Tennessee and Oak Ridge National Laboratory have come up with the first comprehensive measurements of a particle beam. This could help scientists optimize the technique and equipment required to generate particles beams, enhancing their efficiency and enabling yet more intense beams to be produced.

6 Parameters That Describes A Particle Beam

1. Horizontal position of the particle in the beam cross section.
2. Vertical position of the particle in the beam cross section.
3. Particle Momentum towards horizontal position.
4. Particle Momentum towards vertical position.
5. Energy of the particle.
6. Phase of the particle, which is measured by its arrival time at a detector.

Radio-frequency quadrupole is accelerating component of hydrogen ions, and responsible for the beam structure | Courtesy of researchers

Thus, there are a total of 6 coordinates (six-dimensional distribution) to fulfill the description of the beam. Previous studies were able to measure 4 of these parameters at once. They relied on the hypothesis that all parameters are independent of each other.

In this work, researchers have investigated the negative hydrogen ion beam of an accelerator-based neutron source facility, Spallation Neutron Source, at Oak Ridge.

This new technique utilizes 6 adjustable slits situated along the beamline. Every one of them admits only those particles whose parameter values lie within a narrow range. In energy-measuring slit, researchers used magnetic fields to divert the beam. The angle of diversion is based on energy, therefore only particles having a specific range of energies can pass through the energy slit.

Principle behind a complete 6D emittance scan | Courtesy of researchers 

Reference: Physical Review Letters | doi:10.1103/PhysRevLett.121.064804

This technique allows different slits to be gradually scanned through each of these six parameters. At the end of the slits, the particle detector slowly generates an image of the six-dimensional distribution. Within 32 hours, they collected over 5.5 million data points throughout the six-dimensional coordinate space.

Are these 6 parameters truly independent? 

The distribution of particle energy could rely on particle’s position within the beam cross section. Discovering relationships in this 6D space has been quite challenging so far. In this case, researchers have found a presence energy-position relationship by analyzing lower-dimensional data.

Researchers also mentioned that scanning fewer dimensions takes much less time. They performed five-dimensional scans in 4 hours.

Furthermore, there is one other promising technology (currently being developed) to characterize the longitudinal properties of an electron group in a linear accelerator.

Read: New Method For Generating Ultrashort, High-Power Laser Pulses

How It’s Useful?

Since we’ve now access to a complete six-dimensional measurement, we can accurately simulate realistic beam parameters. This will enhance operations of current instruments and enable efficient, high-powered accelerators.