Tuner system Zhenghui MI 2017/01/17

Introduction Tuner design Vertical test CDR (Tuner) Others

Tuner design General •  SRF cavities require frequency tuning systems regardless of their application. The uncertainties in cool-down shifts are typically too large to be acceptable. Furthermore, in case of malfunctions in a cavity, one would like to be able to de-tune it from resonance. These are one-time adjustments, without speed requirements, with large range (large forces, large travel). Specific •  In pulsed regime, the behavior of an SRF cavity is dominated by Lorentz force detuning. Maintaining the cavity locked onto the design frequency may require a fast pulse-to-pulse compensation from the tuner, typically with a small range. •  In CW regime instead the behavior is dominated by fluctuations in the Helium bath pressure which require a slow compensation.

Tuner design Small Bandwidths •  For cavities with bandwidths increasingly small, you will need to adjust the frequency with more and more fine resolution. (e.g. Hertz = nanometers!). Requires microscopic and repeatable motions which are hard to achieve with motors and complex mechanisms •  Resolution requirements are tightly correlated with hysteresis requirements. You can’t achieve high resolution control if you have hysteresis issues (i.e. a backlash/delay between actuation and frequency changes). •  Small bandwidths require silent systems during operation. You may have problems actuating motors during beam-time due to vibrations.

Active and Passive control •  Active control of frequency refers to a feedback system and actuation devices to compensate the causes of shifts in the cavity. •  Passive control involves all those methods aimed at making the cavity less susceptible to perturbations or at reducing the perturbations (e.g. He pressure regulation). •  For cavities with small bandwidths, passive control is imperative.

Tuner survey Scissors Tuner tuner for CEBAF Upgrade Tuner for HWR Cavity FRIB Tuner for ADS Spoke cavity Example CEBAF (1986) to CEBAF Upgrade (2008) Advantage Motor and Piezo are both installed outside of Cryomodule.

Existing tuner-2 Blade Tuner original Blade Tuner Revision of a lighter Blade Tuner New design of the Blade Tuner Working principle Advantage Simple structure and low cost. 25N/um

Existing tuner-4 Saclay tuner 60N/um original Saclay Tuner Modified Saclay Tuner Saclay tuner for ESS Working principle Advantage piezo always compressed high reliability

Existing tuner-5 SNS tuner

Existing tuner-6 LCLSII tuner

Existing tuner-7

tuner parameters Parameters of tuner for 1.3GHz cavity

The consideration for CEPC tuner Tuner Installation Tuner structure is simple and easy to install； Installed at the end of cavity (avoid interference with magnetic shielding)； high reliability and strong maintainability Tuner Performance

The consideration for CEPC tuner Working principle Mechanical interface is simple Large reduction ratio High reliability Mechanical structure One motor + Two Piezoes Motor and Piezoes at the same side

Tuner design Main parameters of tuner 650MHz cavity + tuner Unit Booster tuners Main ring tuners Operation frequency MHz 1300 650 Cooling-down uncertainties kHz 50 Beam loading ＜0.7 ~ 0.32/0.78 LFD ~ 0.4 ~ 0.3 Detuning protection 200 Tuner parameters Coarse (slow) tuner frequency range 400 Coarse tuner frequency resolution Hz ＜ 20 Fine (fast) tuner frequency range ＞ 2 ＞ 1.5 Fine tuner frequency resolution 2 Motor and Piezo working temperature K 5~10 Motor number —— 1 Piezo number 650MHz cavity + tuner 1.3 GHz cavity tuner

VT system Magnetic measurement instrument Prepare for superconducting cavity expulse flux research

Tuner test stand For CEPC Tuner test: ① Use the cryomodule in the NO.1 building ② Use the vertical test Dewar Fermilab tuner test SNS tuner life test Piezo tuner test stand

CDR

Others Tuner Bellow Coupler 650 MHz Cavity string （Cavity + Coupler + tuner）

1.3 GHz 9 cell cavity 1.3 GHz 2 cell cavity

谢 谢！