KEKB HER Stored 19 mA Electron Beam and Positron Beam reached close to LER

[Japanese]

After we stored an 8 GeV electron beam first time in HER(High Energy Ring)on December 13th, the KEKB commissioning group had been working very hard until December 27th to understand the machine and increase the beam intensity. On December 26th, we could store 19 mA in HER. In the morning of 27th, a 3.5 GeV positron beam was successfully transported through the transport line down to injection septum magnets of LER (Low Energy Ring).
The position and intensity of the positron beam through the transport line is shown in Fig. 1. The operation of KEKB stopped on December 27th and will resume on January 8th.

Fig 1. Display of the position and intensity of the positron beam through the transport line at 8:49 on December 27th. The beam was transported over 1100 m from the gun to the injection point to LER.

On December 23rd, the double-slit interferometer, which was installed in HER to measure the beam size, started working. We observed clearly interference patterns both in horizontal and vertical directions as shown in Fig.2. The peak-to-valley ratio of the patterns is a good measure of the beam size.

Fig 2. Vertical and horizontal interference patterns of an electron beam observed by the double-slit interferometer in HER.

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