Overall Design of the ADS Injector I Cryogenic System in China

Blue large-amplitude pulsators (BLAPs) are hot low-mass stars that show large-amplitude light variations likely due to radial oscillations driven by iron group opacities. Period changes provide evidence of both secular contraction and expansion among the class. Various formation histories have been proposed, but none are completely satisfactory. Zhang et al. proposed that the merger of a helium-core white dwarf with a low-mass main-sequence star (HeWD+MS) can lead to the formation of some classes of hot subdwarfs. We have analyzed these HeWD+MS merger models in more detail. Between helium-shell ignition and full helium-core burning, the models pass through the volume of luminosity–gravity–temperature space occupied by BLAPs. Periods of expansion and contraction associated with helium-shell flashes can account for the observed rates of period change. We argue that the HeWD+MS merger model provides at least one BLAP formation channel.

The Formation of Blue Large-amplitude Pulsators from White-dwarf Main-sequence Star Mergers

High power input couplers are key components of the superconducting system for China Accelerator Driven sub-critical System (C-ADS) project. For the first phase, C-ADS includes four types of superconducting cavities (SCCs) of two frequencies, 162.5 MHz HWR SCC and 325 MHz Spoke SCC up to the energy of 25 MeV. All input couplers for the SCCs are developed in IHEP. This paper will describe the development status of the high power input couplers for C-ADS.

https://inspirehep.net/files/fd676e79cd2ebe39d2f41b2d205c45dc

High Power Input Couplers for C-ADS

Abstract We report the discovery of a new Blue Large-Amplitude Pulsator, SMSS J184506-300804 (SMSS-BLAP-1) in Data Release 2 of the SkyMapper Southern Sky Survey. We conduct high-cadence photometric observations in the u band to confirm a periodic modulation of the lightcurve. SMSS-BLAP-1 has a ∼19-min pulsation period with an amplitude of 0.2 mag in u band, and is similar to the classical BLAPs found by OGLE. From spectroscopic observations with the Wide-Field Spectrograph on the ANU 2.3m telescope, we confirm it as a low-gravity BLAP: best-fit parameters from the non-LTE Tlusty model are estimated as Teff = 29,020$^{+193}_{-34}$ K, log g = 4.661$^{+0.008}_{-0.143}$ (cm s−2), and log n(He)/n(H) = -2.722$^{+0.057}_{-0.074}$ dex. However, our BLAP exhibits a very He-deficient atmosphere compared to both low- and high-gravity BLAPs, which have log n(He)/n(H) in the range -0.41∼-2.4. 

Discovery of a new blue large-amplitude pulsator in the SkyMapper DR2: SMSS J184506.82-300804.7

An accelerator-driven system (ADS), which combines a particle accelerator with a subcritical core, is commonly regarded as a promising device for the transmutation of nuclear waste, as well as a potential scheme for thorium-based energy production. So far the predominant choice of the accelerator for ADS is a superconducting linear accelerator (linac). This article gives a brief overview of ADS based on linacs, including the motivation, principle, challenges and research activities around the world. The status and future plan of the Chinease ADS (C-ADS) project will be highlighted and discussed in depth as an example.

ADS Based on Linear Accelerators

Blue large-amplitude pulsators (BLAPs) are a newly discovered type of variable star. Their typical pulsation periods are on the order of a few tens of minutes, with relatively large amplitudes of 0.2-0.4 mag in optical bands, and their rates of period changes are on the order of 10 − 7 yr − 1 (both positive and negative). They are extremely rare objects and attempts to explain their origins and internal structures have attracted a great deal of attention. Previous studies have proposed that BLAPs may be pre-white dwarfs, with masses around 0 . 3 M (cid:12) , or core-helium-burning stars in the range of ∼ 0 . 7 − 1 . 1 M (cid:12) . In this work, we use a number of MESA models to compute and explore whether BLAPs could be explained as shell helium-burning subdwarfs type B (SHeB sdBs). The models that best match existing observational constraints have helium core masses in the range of ∼ 0 . 45 − 0 . 5 M (cid:12) . Our model predicts that the positive rate of period change may evolve to negative. The formation channels for SHeB sdBs involve binary evolution and although the vast majority of BLAPs do not appear to be binaries (with the exception of HD 133729), the observational constraints are still very poor. Motivated by these ﬁndings, we explored the Roche lobe overﬂow channel. Of the 304 binary evolution models we computed, about half of them are able to produce SHeB sdBs in long-period binaries that evade detection from the limited observations that are currently available.

/pdf/shell-helium-burning-hot-subdwarf-b-stars-as-candidates-for-2xw9hhn0.pdf

Shell helium-burning hot subdwarf B stars as candidates for blue large-amplitude pulsators

The ADS proton linac adopts £=0.12 superconducting Spoke cavities. Each cavity is powered via a 325 MHz coaxial power coupler. The coupler is to feed 6 kW maximum power though it is designed to handle at 15 kW .Two coupler sets have been made by IHEP so far, and a 10 kW RF power in continuous travelling wave mode has passed through the coupler during high power test in late January 2013. An introduction of this coupler design and the room temperature test results are presented in this paper.

/pdf/development-of-power-coupler-for-superconducting-spoke-2gqpedpsrq.pdf

Development of Power Coupler for Superconducting Spoke Cavities for China ADS Proton Linac

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Shell helium-burning hot subdwarf B stars as candidates for blue large-amplitude pulsators

Development of Power Coupler for Superconducting Spoke Cavities for China ADS Proton Linac