10 The Largest Accelerators and Colliders of Their Time
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of the electrodes and the electronics were carefully done for the high-current
operation.
• Beam-based alignment of BPMs was regularly carried out. Displacements
of BPMs near sextupoles, caused by heating from the stored current, were
monitored at KEKB [153].
• Bunch-by-bunch feedback systems were installed both in PEP–II and KEKB.
Only PEP–II had the longitudinal system to suppress the beam-loading instability
as described above. A collaboration including the DANE team has been
developed on the system for the present and future applications [154].
• Betatron tune monitor: controlling the betatron tune was extremely important to
maximize the luminosity. The basic idea at KEKB was to monitor the tunes of
pilot bunches in each ring that did not collide to the other beam. Tune feedback
with these bunches was also applied to control them within an accuracy of
ν ≈ 10 −4 .
• Synchrotron radiation beam profile monitors. For the visible light, an interferometer was used especially for the vertical size measurement [155]. Special gated
cameras were also used to observe the beam size of individual bunch, esp. to
diagnose the electron-cloud effects [156].
• Beam loss monitors and beam abort system: both machines were very nervous
to protect the machine against accidental beam losses caused by instabilities,
RF trips, wrong injection, or whatever. The most sensitive and expensive loss
monitor was the BaBar and Belle detectors, which generated beam abort signals
if necessary. A number of beam loss monitors such as ionization chambers and
PiN diodes were distributed around the ring, esp. near the collimators. The beam
abort system consists of an abort kicker and a beam damp. The abort kicker had
a rise time of 0.5 μs in the case of KEKB.
• The injectors had developed their own diagnostics including BPMs, wire scanners, streak cameras, etc.
• All accelerator components were controlled by computer control systems either
by EPICS at KEKB [157] or a legacy system at PEP–II. An online modeling such
as SAD for KEKB [149] was also important to achieve the luminosity.
10.4.9 Collision Tuning
Starting up the colliders after a period of long shut down, the following procedures
were necessary to recover the luminosity:
• Global coupling/dispersion/β-function correction all over the ring. The global
orbit was then locked to the “golden” orbit that was resulted by the optics
correction.
• Locking the betatron tunes of the pilot bunches.
• The beam steering at the IP looking at the beam-beam deflection.
627
of the electrodes and the electronics were carefully done for the high-current
operation.
• Beam-based alignment of BPMs was regularly carried out. Displacements
of BPMs near sextupoles, caused by heating from the stored current, were
monitored at KEKB [153].
• Bunch-by-bunch feedback systems were installed both in PEP–II and KEKB.
Only PEP–II had the longitudinal system to suppress the beam-loading instability
as described above. A collaboration including the DANE team has been
developed on the system for the present and future applications [154].
• Betatron tune monitor: controlling the betatron tune was extremely important to
maximize the luminosity. The basic idea at KEKB was to monitor the tunes of
pilot bunches in each ring that did not collide to the other beam. Tune feedback
with these bunches was also applied to control them within an accuracy of
ν ≈ 10 −4 .
• Synchrotron radiation beam profile monitors. For the visible light, an interferometer was used especially for the vertical size measurement [155]. Special gated
cameras were also used to observe the beam size of individual bunch, esp. to
diagnose the electron-cloud effects [156].
• Beam loss monitors and beam abort system: both machines were very nervous
to protect the machine against accidental beam losses caused by instabilities,
RF trips, wrong injection, or whatever. The most sensitive and expensive loss
monitor was the BaBar and Belle detectors, which generated beam abort signals
if necessary. A number of beam loss monitors such as ionization chambers and
PiN diodes were distributed around the ring, esp. near the collimators. The beam
abort system consists of an abort kicker and a beam damp. The abort kicker had
a rise time of 0.5 μs in the case of KEKB.
• The injectors had developed their own diagnostics including BPMs, wire scanners, streak cameras, etc.
• All accelerator components were controlled by computer control systems either
by EPICS at KEKB [157] or a legacy system at PEP–II. An online modeling such
as SAD for KEKB [149] was also important to achieve the luminosity.
10.4.9 Collision Tuning
Starting up the colliders after a period of long shut down, the following procedures
were necessary to recover the luminosity:
• Global coupling/dispersion/β-function correction all over the ring. The global
orbit was then locked to the “golden” orbit that was resulted by the optics
correction.
• Locking the betatron tunes of the pilot bunches.
• The beam steering at the IP looking at the beam-beam deflection.