We are reproducing the sources for these two big accelerators right in our basement of Newman Lab.” “We are testing the electron sources that are going into these machines, in exactly the same conditions in which they will be used. Or for high-energy physics, like making a “Higgs factory” for example, whose primary job is to produce lots of Higgs bosons for precision studies of the particle.” “We are going to be testing the electron sources for the world’s largest colliders,” says Jared Maxson, For nuclear physics, like the electron-ion collider. To generate these sub-atomic particles, researchers need high-average current electron beams, like those produced in HERACLES. This large collider will search for quarks and gluons, the particles that form the protons and neutrons in visible matter.

One such environment, explains Maxson, is the proposed electron-ion collider to be built at Brookhaven National Lab. Maxson, along with Professor Ivan Bazarov, is leading this effort. “Now that photocathodes are getting better, we can use them in these very brutal industrial environments.” says Jared Maxson, Assistant Professor of physics in the College of Arts and Sciences. The commissioning results of HERACLES are presented in a recent publication. Leading this charge are CLASSE Researchers and graduate students who have built HERACLES in Newman Laboratory to improve the strength of photocathodes developed for high current beam operation. Researchers at Cornell study these photocathodes by recreating the harsh, yet real-world, environments within HERACLES, while trying to minimize the effects of chemical poisoning and ion-back bombardment. This effect causes the positively charged ions to accelerate towards the cathode causing further damage. What’s even more problematic, says Andorf, is an effect called ion-back bombardment, where the electron beam itself leads to the ionization of gas molecules inside the electron gun. The result is known as chemical poisoning. Despite this, remaining residual gas can chemically react with the cathode, degrading its efficiency and damaging the material. Similar to those at large colliders, the HERACLES beamline is constantly maintained in ultra high vacuum.

“So, our photocathodes do not necessarily fail, it’s that we ask a lot of them under extreme conditions.” “The inside of an electron gun is a harsh environment,” says Matt Andorf, research associate in the Cornell Laboratory for Accelerator-based Sciences and Education, CLASSE. However, the efficiency of the photocathode is sensitive to the vacuum environment inside the accelerator, and can degrade rapidly at high current. In machines that do not use electron collisions, a high current electron beam can still improve luminosity by enabling particle beam cooling. A higher beam current yields a larger luminosity, increasing the rate of new physics discoveries. For example, a robust photocathode can sustain a high current electron beam in particle colliders, where one of the most important criteria is beam luminosity, or number of particle collisions produced. Originally designed during the university's Energy Recovery Linac program, the electron gun at the heart of HERACLES has set records for photoinjector current, allowing researchers to study cathodes that can be used in everything from semiconductor manufacturing to the future electron-ion collider.Īccelerator technology relies on photocathodes to produce high-current electron beams for a variety of applications.

Cornell is breaking new ground in electron beam research with the HERACLES beamline, a state-of-the-art electron gun that mimics the harsh environments of the world’s largest particle colliders.

Electrophoresis cathode charge