• Y. Hayashi, S.V. Bulanov, T. Homma, M. Kando, K. Kawase, H. Kotaki
  JAEA, Kyoto

Para­met­ric X-ray gen­er­a­tion is one of the ways to ob­tain a monochro­mat­ic X-ray. The X-ray is gen­er­at­ed through the in­ter­ac­tion be­tween high en­er­gy elec­trons and a crys­tal. The re­la­tion­ship be­tween an X-ray wave­length and an angle of emis­sion is fol­lowed by the Bragg con­di­tion. There­fore the monochro­mat­ic en­er­gy of the X-ray can be var­ied con­tin­u­ous­ly by ro­tat­ing the crys­tal. This tun­abil­i­ty of X-ray wave­length is suit­able for var­i­ous ap­pli­ca­tions. Usu­al­ly a sin­gle pho­ton count­ing method is uti­lized for mea­sur­ing of the para­met­ric X-rays. Al­though this method has an ad­van­tage to ob­tain clear en­er­gy spec­trum, it takes long time. Here, we have mea­sured 10 keV para­met­ric X-rays with ap­ply­ing a rock­ing curve method. In this scheme, a large num­ber of para­met­ric X-rays are de­tect­ed si­mul­ta­ne­ous­ly. This en­ables us to find and tune the para­met­ric X-ray quick­ly. As a re­sult, we could find the sharp peak from this method with the Mi­crotron ac­cel­er­a­tor (150MeV, 20 - 30 pC) at JAEA and a Si crys­tal. Since the peak angle is con­sis­tent to the Bragg con­di­tion for the 10 keV para­met­ric X-ray gen­er­a­tion, we think 10 keV pho­tons have been gen­er­at­ed through the para­met­ric X-ray mech­a­nism.

• H. Kotaki, S.V. Bulanov, Y. Hayashi, T. Homma, M. Kando, K. Kawase, J. Koga, M. Mori
  JAEA, Kyoto

Laser wake­field ac­cel­er­a­tion (LWFA) is re­gard­ed as a basis for the next-gen­er­a­tion of charged par­ti­cle ac­cel­er­a­tors. In ex­per­i­ments, it has been demon­strat­ed that LWFA is ca­pa­ble of gen­er­at­ing elec­tron bunch­es with high qual­i­ty: quasi-mo­noen­er­get­ic, low in emit­tance, and a very short du­ra­tion of the order of ten fem­to-sec­onds. Such fem­tosec­ond bunch­es can be used to mea­sure ul­tra­fast phe­nom­e­na. In ap­pli­ca­tions of the laser ac­cel­er­at­ed elec­tron beam, it is nec­es­sary to gen­er­ate a sta­ble elec­tron beam and to con­trol the elec­tron beam. A 40 fs laser pulse with the en­er­gy of 200 mJ is fo­cused onto a su­per­son­ic gas jet. We suc­ceed to gen­er­ate a sta­ble elec­tron beam by using a Ni­tro­gen gas tar­get. The pro­file of the elec­tron beam can be ma­nip­u­lat­ed by ro­tat­ing the laser po­lar­iza­tion. When we use a S-po­lar­ized laser pulse, a 20 MeV elec­tron beam is ob­served with an os­cil­la­tion in the image of the en­er­gy spec­trum. From the os­cil­la­tion, the pulse width of the elec­tron beam is cal­cu­lat­ed to at most a few tens fs. The di­rec­tion of the elec­tron beam can be con­trolled by chang­ing the gas-jet po­si­tion. The self-in­ject­ed elec­tron beam can be con­trolled by the con­trol of the laser and gas jet.

Slides