Effects of slots/holes in disks on frequencies of TM01 and EH11 waves in disk-loaded waveguides

It has been proven that the combination of boring four holes in each disk at certain radial positions R_c and properly reducing the cavity diameter 2b can make the frequency of the $\text{2π}\text{3}$ mode for TM₀₁ waves invariable and the frequency band for EH₁₁ waves rising with respect to the case without holes in the disks. Taking the SLAC no. 4 cavity as an example, when R_c = 28 mm and the hole diameter 2h = 9 or 11 mm as well as d(2b) = ?0.12 or ?0.28 mm, the operating frequency ($\text{2π}\text{3}$ mode and TM₀₁ wave) remains at 2856 MHz but the EH₁₁ wave frequency band will move up to about 5.5 or 11 MHz with respect to the case without holes in the disks respectively. Obviously, this technique, for example, could be used in Nos. 3, 4 and 5 cavities of the SLAC constant gradient structures for substantially increasing the BBU threshold current of the high energy electron linac using SLAC sections as the accelerating tubes.