Jury Tampering? A term Republicans should acquaint themselves with before the Senate trial.

[The Velveteen Ocelot]

4. There is nothing in the Senate rules providing for the recusal or removal of

Senators in an impeachment trial, or relating to witness tampering or intimidation. https://www.law.cornell.edu/background/impeach/senaterules.pdf The statute you cite is part of the chapter on federal criminal trials, which an impeachment trial is not. It's its own thing. It's not a normal trial and the Senate isn't a normal jury. Senators can be called as witnesses, though, and can submit written questions to be asked of witnesses or offer motions and orders, things that jurors in regular court trials can't do.

XVIII. If a Senator is called as a witness, he shall be sworn, and give his testimony standing in his place.
XIX. If a Senator wishes a question to be put to a witness, or to a manager, or to counsel of the person impeached, or to offer a motion or order (except a motion to adjourn), it shall be reduced to writing, and put by the Presiding Officer. The parties or their counsel may interpose objections to witnesses answering questions propounded at the request of any Senator and the merits of any such objection may be argued by the parties or their
counsel. Ruling on any such objection shall be made as provided in Rule VII. It shall not be in order for any Senator to engage in colloquy.