What to do if i do not want my dental hygienist to use the ultrasonic scaler?

Hand scaling: Ask that your teeth be cleaned with hand scalers.

Combo is the best: Your concern is not uncommon. Hand scaling instruments produce smoother root surfaces compared to ultrasonic scaling, but they don't reduce inflammation, a primary goal of periodontal cleaning and prophylaxis. According to evidence-based dentistry the combined use of ultrasonic scalers and hand instruments will give you the best results. Of course you can always request the manual scaling only

A professional: That does a procedure every day gets good at what he does, asking him to change methods might not produce his best work.