It is the 4th day of Frontier Communicator Internship on July 16. Three interns has started writing the article of ILC NewsLine.
One of the interns, Hiroto Oishi send researchers who he made a interview email to ask the vision of their researches in the future. Ooishi asked during interview “What outcome do you find in this test?” But he didn’t ask “Then, what is your aim of research in the future?” This is an important question. When the science writers do an article of newest researches, they usual write about researcher’s vision in the future end of article. At lunch time, he ate lunch at cafeteria with Jumpei Fujimoto, a scientist at KEK and French scientists. In everyday life of interns, they don’t always have chances of talking with foreign researchers. So this is very good experience for them.
After lunch, Ooishi asked Tsunehiko Omori, a scientist at KEK questions about
International Liner Collider (ILC) and Accelerator Test Facility (AFT). According to Omori, beam energy at AFT2 is 1.28GeV and beam size is 35nm. And at ILC, the values are 250GeV and 6nm. Since beam energy at AFT2 is smaller than that at ILC, beam size at AFT2 is larger than ILC. At AFT2, if we can let beam focus less than 35nm, we can do that less than 6nm at ILC. In addition, Omori lectured Oishi about the shape of beam. At ILC, the beam size of longitudinal is 6nm, you know. But the beam size of transverse is 300nm. Why is the between longitudinal and transverse size of beam difference? The answer is relation to luminosity and electron beam-positron beam interaction because of Coulomb force. We want to let electron and positron beam to impinge. So we want to high Luminosity. Then, section area is smaller, the better the luminosity. But, if we make too small section area beam, the beam of electron and positron interact strong force at interaction point. Then, both beam starts oscillation and will be unstable. We must make large circumferential length of section area beam to attenuate Coulomb interaction. So, we must find point that get on a well of two beams. That is reason for the shape of beam at ILC (and AFT2, too.). Many experimental things have reasons that aren’t obvious on the face of it.