Kangyu Wang

We report the design and characterization of a CMOS pixel direct charge sensor, Topmetal-II-, fabricated in a standard 0.35 μm CMOS Integrated Circuit process. The sensor utilizes exposed metal patches on top of each pixel to directly collect charge. Each pixel contains a low-noise charge-sensitive preamplifier to establish the analog signal and a discriminator with tunable threshold to generate hits. The analog signal from each pixel is accessible through time-shared multiplexing over the entire array. Hits are read out digitally through a column-based priority logic structure. Tests show that the sensor achieved a <15e- analog noise and a 200e- minimum threshold for digital readout per pixel. The sensor is capable of detecting both electrons and ions drifting in gas. These characteristics enable its use as the charge readout device in future Time Projection Chambers without gaseous gain mechanism, which has unique advantages in low background and low rate-density experiments.

This thesis investigates hard choices—decision-making cases in which an agent’s options are incommensurable—and what their rise and resolution reveal about practical reason, the self, and human and non-human agency. I develop my arguments on three distinct but connected levels: the formal structure of hard choices, the mechanisms underlying them, and the practical reasons involved. In Chapter 0, I lay out these three levels and introduce my account of incommensurability. In Chapter 1, I consider which theory of practical reason can make sense of the resolution of hard choices. I critically examine reason externalism and Ruth Chang’s hybridism of reason and conclude that reason internalism is the best candidate. In Chapter 2, the core chapter of this thesis, I argue that hard choices arise from multiple permissible perspectives and that resolving a hard choice, for a human agent, means remaking oneself by moderating one’s desires. I argue that this process is rational and agentic in one sense, pre-rational and sub-agentic in another. In Chapter 3, I turn to the puzzling phenomenon that arbitrary picking is unfitting in some hard choices but not others. I reject five existing explanations and defend my own account involving Williamsian integrity and the deep-self. In Chapter 4, I pivot to the intersection between decision theory concerning incommensurability and dynamic decision theory and argue that neither Richard Pettigrew’s Aggregate Utility Solution nor similar aggregate solutions can satisfactorily accommodate incommensurability. In Chapter 5, I consider AI agents, demonstrating that under existing technological frameworks they are unable to identify or resolve hard choices, and reflect on the implications for alignment and the distinctiveness of human agency. Chapter 6 summarises the thesis and considers directions for future research.