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Electromagnetic and Mechanical Properties of Medium β SRF Elliptical Cavities.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Electromagnetic and Mechanical Properties of Medium β SRF Elliptical Cavities./
Author:	Contreras-Martinez, Crispin.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2021,
Description:	193 p.
Notes:	Source: Dissertations Abstracts International, Volume: 83-02, Section: B.
Contained By:	Dissertations Abstracts International83-02B.
Subject:	Physics. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28498572
ISBN:	9798534662887

Electromagnetic and Mechanical Properties of Medium β SRF Elliptical Cavities.
Contreras-Martinez, Crispin.

Electromagnetic and Mechanical Properties of Medium β SRF Elliptical Cavities. - Ann Arbor : ProQuest Dissertations & Theses, 2021 - 193 p.

Source: Dissertations Abstracts International, Volume: 83-02, Section: B.

Thesis (Ph.D.)--Michigan State University, 2021.

This item must not be sold to any third party vendors.

The new generation of hadron SRF linac projects to produce rare isotopes and high-intensity neutrinos require developing a new elliptical cavity design optimized for medium β = 0.65 and operating at relatively low frequency, at 650 MHz. During operation, vibration noise (microphonics) causes the cavity to deform, shifting its resonance frequency. Slight deformations of elliptical cavities can significantly detune the cavity frequency from the resonance. A frequency shift in the cavity lowers the nominal accelerating field, which can be compensated either by using additional RF power or both a dedicated fast mechanical tuner and more RF power. In addition, cavities must be designed to reduce sensitivity to microphonics. Microphonics compensation by increased RF power is not economical, especially in low-intensity linacs.The first part of this thesis explores a cost-effective method that uses a tuner consisting of a piezoelectric actuator. The piezoelectric actuator can elastically deform the cavity to track the resonance frequency, thus allowing for efficient use of RF power towards beam acceleration. The development and testing of a new combined slow and fast tuner for the 650 MHz cavity are presented in this thesis. The slow tuning component uses a stepper motor and can compensate for frequency detuning on the order of kHz on the order of seconds. The fast tuning component uses a piezoelectric actuator that can compensate for frequency detuning on the order of Hz and ms. A lumped circuit model to study the resonance response of the cavity in the presence of microphonics is presented. This model incorporates the experimental results of the mechanical modes of the650 MHz cavity for the first time. Lower frequency cavities are larger and more sensitive to microphonics than widely used 1.3 GHz elliptical cavities for the acceleration of electrons. We had an opportunity to study the microphonics properties in the cryomodule setting with eight 1.3 GHz cavities experimentally before the development of a tuner for 650 MHz cavities. A new correlation between various cryogenic parameters and the frequency detuning of 1.3 GHz cavities is presented for multiple cavities in different cryomodules. A tuner that incorporates a piezoelectric actuator is used for the active compensation of microphonics. The piezoelectric properties of actuators for operation in a CW linac are available in the scientific literature. This thesis provides new results for piezo actuators operated at a high voltage needed for large gradient pulsed linacs. This work led to the discovery of large dielectric heating of the piezo and deviation from the dielectric heating formula found in the literature. Large heating of the piezo will result in a reduced lifetime. A discussion on why this deviation occurs is presented. A novel piezoelectric actuator was designed and built, yielding a reduction of heating by a factor of 14 at liquid helium temperatures. The properties of lithium niobate for use in SRF cavity resonance control were tested for the first time. Lithium niobate shows no heating but with a compromise of a smaller stroke. The results pave the way for future optimization of materials with larger stroke but smaller dielectric heating.In the second part of this thesis, two resonance control algorithms were implemented on a single-cell elliptical 1.3 GHz cavity at room temperature. The proportional-integral (PI) loop algorithm was used to compensate for slow varying vibrations (less than 5 Hz). The successful implementation of this algorithm with the single-cell elliptical cavity at room temperature demonstrates that it can control liquid helium pressure variations and other slow varying vibrations of the cavity in the cryogenic environment. For vibrations above 5 Hz, the least mean square (LMS) algorithm was used. The implementation of the LMS algorithm in the FPGA successfully suppressed 2 sinusoidal vibrations by a factor of 3 with white Gaussian noise (0.07 Hz detuning) in a matter of ms. The use of active resonance control will reduce the required cavity RF power and increase the reliability of the linac.

ISBN: 9798534662887Subjects--Topical Terms:

516296
Physics.
Subjects--Index Terms:

Piezoelectric heating

Electromagnetic and Mechanical Properties of Medium β SRF Elliptical Cavities.
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100 1 $a Contreras-Martinez, Crispin. $0 (orcid)0000-0001-8601-0741 $3 3686367
245 1 0 $a Electromagnetic and Mechanical Properties of Medium β SRF Elliptical Cavities.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2021
300 $a 193 p.
500 $a Source: Dissertations Abstracts International, Volume: 83-02, Section: B.
500 $a Advisor: Ostroumov, Peter.
502 $a Thesis (Ph.D.)--Michigan State University, 2021.
506 $a This item must not be sold to any third party vendors.
520 $a The new generation of hadron SRF linac projects to produce rare isotopes and high-intensity neutrinos require developing a new elliptical cavity design optimized for medium β = 0.65 and operating at relatively low frequency, at 650 MHz. During operation, vibration noise (microphonics) causes the cavity to deform, shifting its resonance frequency. Slight deformations of elliptical cavities can significantly detune the cavity frequency from the resonance. A frequency shift in the cavity lowers the nominal accelerating field, which can be compensated either by using additional RF power or both a dedicated fast mechanical tuner and more RF power. In addition, cavities must be designed to reduce sensitivity to microphonics. Microphonics compensation by increased RF power is not economical, especially in low-intensity linacs.The first part of this thesis explores a cost-effective method that uses a tuner consisting of a piezoelectric actuator. The piezoelectric actuator can elastically deform the cavity to track the resonance frequency, thus allowing for efficient use of RF power towards beam acceleration. The development and testing of a new combined slow and fast tuner for the 650 MHz cavity are presented in this thesis. The slow tuning component uses a stepper motor and can compensate for frequency detuning on the order of kHz on the order of seconds. The fast tuning component uses a piezoelectric actuator that can compensate for frequency detuning on the order of Hz and ms. A lumped circuit model to study the resonance response of the cavity in the presence of microphonics is presented. This model incorporates the experimental results of the mechanical modes of the650 MHz cavity for the first time. Lower frequency cavities are larger and more sensitive to microphonics than widely used 1.3 GHz elliptical cavities for the acceleration of electrons. We had an opportunity to study the microphonics properties in the cryomodule setting with eight 1.3 GHz cavities experimentally before the development of a tuner for 650 MHz cavities. A new correlation between various cryogenic parameters and the frequency detuning of 1.3 GHz cavities is presented for multiple cavities in different cryomodules. A tuner that incorporates a piezoelectric actuator is used for the active compensation of microphonics. The piezoelectric properties of actuators for operation in a CW linac are available in the scientific literature. This thesis provides new results for piezo actuators operated at a high voltage needed for large gradient pulsed linacs. This work led to the discovery of large dielectric heating of the piezo and deviation from the dielectric heating formula found in the literature. Large heating of the piezo will result in a reduced lifetime. A discussion on why this deviation occurs is presented. A novel piezoelectric actuator was designed and built, yielding a reduction of heating by a factor of 14 at liquid helium temperatures. The properties of lithium niobate for use in SRF cavity resonance control were tested for the first time. Lithium niobate shows no heating but with a compromise of a smaller stroke. The results pave the way for future optimization of materials with larger stroke but smaller dielectric heating.In the second part of this thesis, two resonance control algorithms were implemented on a single-cell elliptical 1.3 GHz cavity at room temperature. The proportional-integral (PI) loop algorithm was used to compensate for slow varying vibrations (less than 5 Hz). The successful implementation of this algorithm with the single-cell elliptical cavity at room temperature demonstrates that it can control liquid helium pressure variations and other slow varying vibrations of the cavity in the cryogenic environment. For vibrations above 5 Hz, the least mean square (LMS) algorithm was used. The implementation of the LMS algorithm in the FPGA successfully suppressed 2 sinusoidal vibrations by a factor of 3 with white Gaussian noise (0.07 Hz detuning) in a matter of ms. The use of active resonance control will reduce the required cavity RF power and increase the reliability of the linac.
590 $a School code: 0128.
650 4 $a Physics. $3 516296
650 4 $a Applied physics. $3 3343996
650 4 $a Electromagnetics. $3 3173223
650 4 $a Acoustics. $3 879105
650 4 $a Electrical engineering. $3 649834
650 4 $a Simulation. $3 644748
650 4 $a Tensile strength. $3 3564816
650 4 $a Control algorithms. $3 3560702
650 4 $a Experiments. $3 525909
650 4 $a Electric fields. $3 880423
650 4 $a Antennas. $3 3681648
650 4 $a Copper. $3 1070053
650 4 $a Heat. $3 573595
653 $a Piezoelectric heating
653 $a Superconducting radio frequency cavities
653 $a SRF Resonance Control
653 $a Microphonics
690 $a 0605
690 $a 0544
690 $a 0215
690 $a 0986
690 $a 0607
710 2 $a Michigan State University. $b Physics - Doctor of Philosophy. $3 2096747
773 0 $t Dissertations Abstracts International $g 83-02B.
790 $a 0128
791 $a Ph.D.
792 $a 2021
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28498572