Continuous development of the different filling patterns is a long-standing consideration at the ESRF. Moreover, during the year 2000 significant progress was achieved in this domain.

For the first time, beam in uniform filling was delivered in User Service Mode (USM) for one full week. In this mode all bunches are filled. As a consequence, the Touschek lifetime increased in comparison to the 2 x 1/3-filling due to a smaller current per bunch. The total lifetime increased by 10 hours to a record lifetime of 65 hours at 200 mA. This operation mode will become the standard filling pattern whenever there is no time structure required from the beamlines.

The intensity in the single bunch delivery was raised from 16 mA to 20 mA. This was possible after machine tuning and following the removal of some vacuum chambers with high impedance. Even with this higher intensity the lifetime remained the same as before, at 5 hours (with 1.5% coupling).

The year 2000 is quite a good reflection of the whole of 1999, with almost 68% of beam time delivered in the 'high-intensity' modes, i.e., the "2 times 1/3 filling", the Uniform mode and the Hybrid mode. (See Figure 125).

Figure 125
Fig. 125: The filling modes during the year 2000.  

In 1999, the beam was delivered at 4 GeV in USM in order to offer smaller horizontal and vertical emittance. The intensity was limited to 100 mA and the lifetime barely reached 10 hours. Experience at that time showed, however, that the energy chosen was too low and that the photon fluxes were too reduced compared to 6 GeV. Following this experience a second attempt was made in 2000 ­ this time at 5 GeV. The beam was delivered over five shifts to users with an intensity of 190 mA, a 1.7 nm horizontal emittance and a new record vertical emittance of 7 pm. The lifetime at 190 mA was 15 hours. Several beamlines benefited from this test but it is not clear whether this mode will find its place in the next schedule.

In 1999, the horizontal focussing optic was developed which enables minimising the horizontal beam size on the sample. In November 2000, one full week of USM was delivered providing this method of focussing for the ID20 beamline. This was achieved without any drawbacks on beam performances and the photon beam sizes were reduced as expected. The interest of this optic for the experiments on ID20 has, however, still to be fully assessed.