| |
A statistical model for field emission developed in 1993 has been applied to characterize the improvement in field emitter properties and field emitter occurrence due to improvements in treatment methods for 9-cell TESLA-style cavities. The improved treatments are electropolishing, high pressure rinsing and baking (120C, 48 hours). We model the Q vs. Eacc data from 24 9-cell tests and 32 1-cell tests, all conducted at TTF by DESY. The statistical model is able to successfully simulate the observed yields by applying a factor of 3 decrease in emitter density over the emitter density prevailing for treatments in 1993, which did not include high pressure rinsing. Both simulation and data show that at Eacc = 70 MV/m the yield for field emission power less than 100 watts (Q > 8x109) is less than 20%. To raise this yield to 80% will require new treatments that will reduce the emitter density by another factor of 3 at least. Further comparisons of field emission behavior will be made with data for alcohol rinsed cavities.
|
|