ANL, Argonne, USA
Purdue University, West Lafayette, Indiana, USA
The first prototype superconducting undulator (SCU0) was successfully installed and commissioned at the Advanced Photon Source (APS) and is delivering photons for user science. All the requirements before operating the SCU0 in the storage ring were satisfied during a short but detailed beam commissioning. The cryogenic system performed very well in the presence of the beam. The total beam-induced heat load on the SCU0 agreed well with the predictions, and the SCU0 is protected from excessive heat loads through a combination of orbit control and SCU0 alignment. When powered, the field integral measured with the beam agreed well with the magnet measurements. An induced quench caused very little beam motion, and did not cause loss of the beam. The device was found to quench during unintentional beam dumps, but quench recovery is transparent to storage ring operation. There were no beam chamber vacuum pressure issues and no negative effect observed on the beam. Finally, the SCU0 was operated well beyond its design requirements, and no significant issues were identified. The beam commissioning results are described in this paper.
ANL, Argonne, USA
Purdue University, West Lafayette, Indiana, USA
The first prototype superconducting undulator (SCU0) was successfully installed and commissioned at the Advanced Photon Source (APS) and is delivering photons for user science. The cryosystem was designed to handle a beam-induced heat load of up to 40 W. Prior to operations, detailed predictions of this heat load were made, including that produced by resistive wall heating by the image current, geometric wakefields, synchrotron radiation, electron cloud, and beam losses. The dominant cw source is the resistive wall heat load. The heat load predictions for standard 100 mA user operation were benchmarked using thermal sensors that measure temperatures at various locations in the SCU0 cryostat and along the electron beam chamber. Thermal analysis using the predicted heat loads from the electron beam, using three independent methods, agrees well with the observed measurements.
ANL, Argonne, USA
A cryocooler-cooled superconducting undulator (SCU0) has been built and cryogenic and magnetic test has been completed. The device is currently installed in the Advanced Photon Source (APS) beam line. The device consists of a dual-core 42-pole magnet structure which is cooled to 4.2 K with a system of four cryocoolers operating in a zero-boil-off configuration. In this paper, a thermal model of the beam chamber and its cooling circuit are presented. A temperature profile of the cooling circuit and heat load to cryocoolers are calculated based on steady state temperatures. Comparison with cryogenic test results and future improvement will be discussed.
ANL, Argonne, USA
Magnetic measurement systems for accelerator magnets typically use relatively complicated rigid rotating coils and digital integrators to capture the integrated coil signal as a function of angular position of the coil. This technique has proven to be reliable and accurate for measuring the field quality of conventional multipole magnets; however, the design and construction of the rotating coils ultimately determine the accuracy of the measurement system. A different concept and implementation of a simple stretched-wire rotating coil will be described. This system utilizes a single-turn radial coil continuously rotating at a fixed angular velocity. The coil signal and a reference pulse are sampled with a 24-bit ADC. A lock-in technique or an FFT can be used to determine the harmonic content of the signal and thus calculate the main field strength and angle, multipole coefficients, and magnetic center offsets. The main advantages of such a system are ease of coil manufacturing and simple mechanical system design.
ANL, Argonne, USA
A superconducting (SC) undulator prototype designated SCU0 was installed in the APS storage ring in December, 2012, and is providing users with photons in the energy range of 80-100 keV. This device was assembled and tested during the majority of 2012. Detailed tests were performed related to cryogenics, vacuum, mechanical motion due to thermal contraction, and magnetic performance. Magnetic measurements have been performed using a horizontal measurement system, which utilizes Hall probes and an integral coil. The measurement system was configured without interfering with the cryogenic or vacuum systems of the SCU0 cryomodule. Some of the magnetic measurement results will be presented for local and integrated field measurements, integrated field uniformity, and integrated fields during a quench. The measured rms phase errors were typically less than two degrees. The measured change in the integrated field during an intentional quench was less than 35 G-cm. The magnetic performance of SCU0 has proven to be within design tolerance for field quality and quench characteristics. Beam-based integral measurements agree well with the magnetic measurements.