Particle accelerators

Particle beam steering with bent crystals

Bent crystals

In a curved crystal, channeled particles are forced to follow the curvature of the crystal, as if they were following "tracks."

This effect can be used to deflect high energy particle beams with unparallel power

Channeling phenomenon

The behavior of particles in matter varies dramatically between amorphous materials and crystals. In crystals, atoms align in specific orientations along well-defined planes and axes. This ordered structure creates a continuous potential for incoming particles, replacing random, stochastic interactions with individual atoms.

Amorphous or randomly oriented crystal

oriented crystal

Channeling in bent crystals

Strong static potential (≈GeV/cm) can trap (channel) positive particles between two adjacent atomic planes angle

Channeled particles are forced to follow crystal curvature, with steering power ≈ 100T magnetic dipole

Ferrara's lab activities

At our lab, we have developed advanced techniques to bend crystals, tailoring their structure to specific experimental needs. By using high-precision X-ray diffraction with our state-of-the-art diffractometer, we can directly measure the curvature of lattice planes with exceptional accuracy. This allows us to fine-tune the crystal properties, enhancing the precision and reliability of our experiments

One of the group's proudest achievements is this dynamic holder, capable of mechanically bending a 15-micron-thin silicon membrane in real time using a piezoelectric actuator.

This innovation enables precise control over the curvature of thin crystals, which have been successfully tested with particle beams.

Bent crystal applications

BENT CRYSTAL INSTALLED AT LARGE HADRON COLLIDER

In the Large Hadron Collider (LHC), even a tenth of a billionth of the beam energy can induce quenching, potentially destroying the superconducting magnets that guide particles around the 27 km ring. This highlights the crucial role of beam collimation, which involves removing stray particles circulating in the accelerator. Collimation becomes increasingly challenging as the particle energy rises. For the LHC's next upgrade, which will double the beam intensity, bent crystals manufactured in Ferrara laboratories will be incorporated into the collimation system. These crystals will exploit channeling to safely divert ions away from the beam orbit and into a dedicated absorber.

TWOCRYST

The Electric and Magnetic Dipole Moment (EDM and MDM) are intrinsic properties of particles which offer powerful insight into their internal structure and discovery of New Physics Beyond the Standard Model. Traditionally, measuring spin precession of a particle travelling in a magnetic field has been used to study EDM/MDM. However, magnets are currently too weak to extend this approach to fast decaying particles which decay after a few centimeters. Channeling in a bent crystal, by contrast, provides fields sufficiently strong to allow this study. The Crystal Lab team is developing bent crystal for the investigation of charmed baryons EDM/MDM at the Large Hadron Collider, proposed by the TWOCRYST collaboration.

Mu2e BEAM DELIVERY

The Mu2e experiment aims to detect whether a muon can transform into an electron and nothing else—an event that would reveal new particles or forces of nature. Since this process is extremely rare, a high-intensity muon beam is essential.
At Fermilab, muons are produced when an 8 GeV proton beam strikes a fixed target. Protons are extracted from the Delivery Ring using an electrostatic septum, which must be well protected to ensure efficient beam delivery and minimize losses and radiation risks. A bent crystal, placed upstream of the septum, can deflect unwanted particles through channeling, reducing potential damage. This innovative instrument is being developed at the Crystal Labs.