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Note 9 - Income Taxes (Details Textual) - USD ($) | 12 Months Ended
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Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2019
Deferred Tax Assets, Tax Credit Carryforwards | $ 1,277,006 | $ 1,437,670 |  |  |
Deferred Income Tax Liabilities, Net | 2,277,550 | 1,890,562 |  |  |
Deferred Income Tax Assets, Net | 617,390 | 771,746 |  |  |
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions | 0 | 273,936 |  |  |
Domestic Tax Jurisdiction [Member] | Internal Revenue Service (IRS) [Member] |  |  |  |  |
Effective Income Tax Rate Reconciliation, Tax Credit, Amortization, Period (Year) |  |  |  | 20 years |
Tax Credit Carryforward, Annual Amortization Amount | 0 | 0 |  |  |
Research Tax Credits, Settlement, Percentage |  |  |  |  | 40.00%
Deferred Tax Assets, Tax Credit Carryforwards, Research | $ 705,848 |  |  |  |
Open Tax Year | 2018 2019 |  |  |  |
Domestic Tax Jurisdiction [Member] | Internal Revenue Service (IRS) [Member] | Research Tax Credit Carryforward [Member] |  |  |  |  |
Deferred Tax Liabilities, Regulatory Assets and Liabilities | $ 2,568,143 |  |  |  |
Domestic Tax Jurisdiction [Member] | Internal Revenue Service (IRS) [Member] | Federal Energy Investment Tax Credit [Member] |  |  |  |  |
Effective Income Tax Rate Reconciliation, Tax Credit, Amortization, Period (Year) |  |  | 20 years |  |
Tax Credit Carryforward, Annual Amortization Amount | $ 127,404 | $ 127,404 |  |  |
Tax Credit Carryforward, Amount |  |  | $ 1,892,164 |  |
Deferred Tax Assets, Tax Credit Carryforwards |  |  | $ 655,862 |  |
State and Local Jurisdiction [Member] | Virginia, Jurisdiction [Member] |  |  |  |  |
Open Tax Year | 2022 2023 2024 2025 |  |  |  |

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- Definition Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, with jurisdictional netting. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482525/740-10-45-4 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482525/740-10-45-6 + Details
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