The changes in the carrying amount of goodwill, by reportable segment, are as follows, in thousands:


	Thermal Processing Solutions		Semiconductor Fabrication Solutions			Total Goodwill
Goodwill	$	5,905	$	21,726		$	27,631
Accumulated impairment losses		—		—			—
Balance at September 30, 2023		5,905		21,726			27,631
Goodwill acquired		—		—			—
Impairment of goodwill		—		(6,370	)		(6,370	)
Balance at September 30, 2024	$	5,905	$	15,356		$	21,261
Goodwill	$	5,905	$	21,726		$	27,631
Accumulated impairment losses		—		(6,370	)		(6,370	)
Balance at September 30, 2024	$	5,905	$	15,356		$	21,261

On January 17, 2023, we acquired Entrepix, which has been integrated into our Semiconductor Fabrication Solutions segment. Under the purchase method of accounting, the purchase price for the acquisition was allocated to the tangible

and identifiable intangible assets acquired and liabilities assumed based on their estimated fair values. The excess purchase price over fair value of net assets acquired of approximately $16.5 million was recorded as goodwill in the Semiconductor Fabrication Solutions segment. The primary driver for this acquisition was to add CMP and wafer cleaning equipment to our existing substrate polishing and wet process chemical offerings.

We review goodwill for impairment when events or circumstances indicate the carrying value may not be recoverable. We performed our annual test of goodwill impairment as of September 30. The results of the goodwill impairment test indicated that the fair value of both our Thermal Processing and Semiconductor Fabrication Solutions reporting units were in excess of the carrying value, and, thus, were not impaired. At the end of December 2023, we identified a triggering event. As a result of the decline in our stock price as of December 31, 2023, our book value materially exceeded our market value leading to a $6.4 million impairment charge in fiscal 2024.

Determining the fair value of a reporting unit involves the use of significant estimates and assumptions. Our goodwill impairment test uses a weighting of the income approach and the market approach to estimate a reporting unit’s fair value. The income approach is based on a discounted future cash flow analysis that uses certain assumptions including: projections of revenues and expenses and related cash flows based on assumed long-term growth rates and demand trends; expected future investments and working capital requirements to sustain and grow the business; and estimated discount rates based on the reporting unit’s weighted average cost of capital as derived by the Capital Asset Pricing Model and other methods, which includes observable market inputs and other data from identified comparable companies. The same estimates are also used internally for our capital budgeting process, and for long-term and short-term business planning and forecasting. We test the reasonableness of the inputs and outcomes of our discounted cash flow analysis against available comparable market data, and we also perform a reconciliation of our total market capitalization to the estimated fair value of all of our reporting units. The market approach is based on the application of appropriate market-derived multiples selected from (i) comparable publicly-traded companies and/or (ii) the implied transaction multiples derived from identified merger and acquisition activity in the market. Multiples are then selected based on a comparison of the reviewed data to that of the reporting unit and applied to relevant historical and forecasted financial parameters such as levels of revenues, EBITDA, EBIT or other metrics. The calculation of fair value falls under Level 3 of the fair value hierarchy.