Table 2. Specifications of current ETCC, ETCC type-A and ETCC type-B.

	current ETCC	ETCC type-A	ETCC type-B
TPC volume	10 cm × 10 cm × 16 cm	20 cm ϕ (in diameter) × 20 cm	30 cm × 30 cm × 30 cm
TPC gas	Ar and C2H6 (90%: 10%) at 1.5 atm	Ar and CF4 (50%: 50%) at 2 atm	CF4 at 3 atm
effective detection area (for 662 keV gammas)	~0.01 cm2	~0.2 cm2	~10 cm2
minimum exposure time	~100 min.	several min.	several sec.

Note that a minimum exposure time is estimated as gammas detected with 2σ significance in each pixel in the condition of 2 μSv/h radiation, which is the same condition as the location (C).