----------------------------------------------------------------
Since the upgrade of the ring involved lots of hardware and software, such as quadrupoles, vacuum chamber, separators, NEG pump, quadrupole power supplies, on-line lattice code and so on, the main task of the first run would be to measure the luminosity to see if it is improved.
According to the experience of other machines, it must take a few months to check the collider after a large-scale upgrade. This time, we did machine study for little more than a month (from May 23 to June 29). After two months' checking, the performance of BEPC ring was remarkably improved, the peak luminosity reaches 1.5 times high as before and the ratio of the signal to noise increases obviously.
From June 20, the linac began to provide beam of 1.548 GeV. After adjustments under off-line and on-line conditions, the beams can be directly injected into the ring from the linac in colliding mode ($\beta^{*}_{y}$=8.5cm).
During the first run, we measured some basical parameters of the ring, such as tunes, $\beta_{x,y}$, $\eta$, $\epsilon$, K and $\sigma$; optimized the colsed orbit, tunes and the working routes; adopted different emittance modes, increased beam currents and luminosity; realized to inject the beams into the ring with the colliding mode; gained the maximum colliding beam current to larger than 40 mA in J/psi enrgy; raised the peak luminosity better than $4x10^{30}cm_{-2}s_{-1}$ (the maximum value is $4.38x10^{30}$), almost 1.5 times high as before, reached the ratio of the signal to noise larger than 130 and made the tune-tune shift higher, i.e, $\delta_{x}=0.045$, $\delta_{y}=0.04$.
For the next run, we will collide beams at single interaction point, increase the beam emittance and optimize operation optics and the closed orbits. With all these done, we hope to raise the luminosity still further.
[ Table of contents | Next Page | Previous Page ]
June 1996 BEPC News